The global_name in an oracle database has a direct impact on the Golden Gate Extract process registration we need to do when we create an Integrated Extract.

In my example below, I use Oracle GoldenGate MicroServices architecture but the same behaviour occurs with Oracle GoldenGate Classic architecture.

Let’s start with the creation of the Extract process by clicking on the plus button :

Choose Integrated Extract and click on Next button:

Fulfill all mandatory fields:

Add the list of tables you want to replicate:

Click on Create and Run the process. After a few seconds, the following error message appears :

An integrated extract must to be registered into the database and this is the registration process which fails.

By checking into the report file, we see that Logmining server does not exist on the database. This error is a consequence of the extract registration process failure.

The problem is Oracle GoldenGate doesn’t support the character “-” in the GLOBAL_NAME:

SQL> select * from global_name;

GLOBAL_NAME
--------------------------------------------------------------------------------
DB1.IT.DBI-SERVICES.COM

SQL> sho parameter db_domain

NAME     TYPE VALUE
------------------------------------ ----------- ------------------------------
db_domain     string it.dbi-services.com

The solution is to modify the db_domain and rename the global_name :

SQL> alter system set db_domain='it.dbiservices.com' scope=spfile;

System altered.


SQL> alter database rename global_name to DB1.ITDBISERVICES.COM;

Database altered.

Let’s now try create the Extract Process:

Now it works :

Let’s check the report file by clicking in Action/details button :

The new global_name (DB1.ITDBISERVICES.COM) is now active  and Logminig server is enabled into the database.

Cet article Oracle GoldenGate 19c: Cannot register Integrated EXTRACT due to ORA-44004 est apparu en premier sur Blog dbi services.

By Franck Pachot

.
Oracle Enterprise Linux (OEL) is a Linux distribution which is binary compatible with Red Hat Enterprise Linux (RHEL). However, unlike RHEL, OEL is open source, free to download, free to use, free to distribute, free to update and gets free bug fixes. And there are more frequent updates in OEL than in CentOS, the free base of RHEL. You can pay a subscription for additional support and features (like Ksplice or Dtrace) in OEL. It can run the same kernel as RHEL but also provides, still for free, the ‘unbreakable kernel’ (UEK) which is still compatible with RHEL but enhanced with optimizations, recommended especially when running Oracle products.

This is not new and I didn’t resist to illustrate the previous paragraph with the animated gif from the years of this UEK arrival. What is new is that OEL is also the base for the new Autonomous Linux which can run in the Oracle Cloud, automates Ksplice for updating the system online, without restart, and sending notifications about these updates. You can use it in the Oracle Cloud Free Tier.

When creating an Always Free compute instance you select the Oracle Autonomous Linux image. I’ve summarized all steps there:

Autonomous Linux image

Generate an API private key

[opc@al ~]$ mkdir ~/.oci
[opc@al ~]$ openssl genrsa -out ~/.oci/oci_api_key.pem 2048 # no passphrase
[opc@al ~]$ chmod go-rwx ~/.oci/oci_api_key.pem
[opc@al ~]$ openssl rsa -pubout -in ~/.oci/oci_api_key.pem -out ~/.oci/oci_api_key_public.pem
writing RSA key

This generates an API key temporarily.

Configure OCI CLI profile

[opc@al ~]$ sudo al-config -u ocid1.user.oc1..aaaaaaaafo2liscovfefeubflxm2rswrzpnnmosue4lczmgaaodwtqdljj3q -t ocid1.tenancy.oc1..aaaaaaaazlv5wxkdhldyvxkkta7rjn25ocovfefexhidte5zgiyauut2i2gq -k ~/.oci/oci_api_key.pem
Configured OCI CLI profile.
Please delete /home/opc/.oci/oci_api_key.pem

This configures the OCI CLI profile for my user (ocid1.user.oc1.. is my user OCID which I find in Oracle Cloud » Governance and Administration » Identity » Users » Users Detail » OCID copy) in my tenancy (ocid1.tenancy.oc1.. is my tenancy OCI I find in Oracle Cloud » Governance and Administration » Administration » Tenancy Details » OCID copy).

Notifications

When something happens autonomously you want to be notified for it. This uses the OCI notification service with a topic you subscribe to. This is also available in the Free Tier. The topic is created with Oracle Cloud » Application Integration » Notifications » Create Topic, where you just put a name and a description and get the OCID for it (ocid1.onstopic.oc1.eu-frankfurt-1… for me).

While in the console, on this topic I’ve created a subscription where I have put my e-mail address. I’ll receive by e-mail all notifications sent to this topic.

Configure OCI notification service topic OCID

[opc@al ~]$ sudo al-config -T ocid1.onstopic.oc1.eu-frankfurt-1.aaaaaaaaamo7khj3xab6oec5xtcovfefeokqszapwsafeje6g6ltlnhd363a
Configured OCI notification service topic OCID.
Publishing message 'AL: Notification enabled on instance AL'
Published message 'AL: Notification enabled on instance AL'

In the Autonomous Linux instance I’ve setup the OCI notification service topic OCID. And that’s all.

Check your e-mails, you have to acknowledge the reception of notifications of course.

Kernel version

[opc@al ~]$ uname -a
Linux al 4.14.35-1902.301.1.el7uek.x86_64 #2 SMP Tue Mar 31 16:50:32 PDT 2020 x86_64 x86_64 x86_64 GNU/Linux

Here is the kernel version that has been installed

[opc@al ~]$ sudo uptrack-uname -a
Linux al 4.14.35-1902.302.2.el7uek.x86_64 #2 SMP Fri Apr 24 14:24:11 PDT 2020 x86_64 x86_64 x86_64 GNU/Linux

This is the effective kernel updated with Ksplice

[opc@al ~]$ sudo uptrack-show
Installed updates:
[cp1p7rl5] Known exploit detection.
[3kfqruxl] Known exploit detection for CVE-2017-7308.
[6vy9wlov] Known exploit detection for CVE-2018-14634.
[r8wncd28] KPTI enablement for Ksplice.
[3e9je971] Known exploit detection for CVE-2018-18445.
[20bmudk6] Out-of-bounds access when classifying network packets with traffic control index.
[oy5cke5u] NULL dereference while writing Hyper-V SINT14 MSR.
[5jsm8lzj] CVE-2020-9383: Information leak in floppy disk driver.
[5p7yd05e] NULL pointer dereference when initializing Differentiated Services marker driver.
[sajmv0xh] CVE-2018-19854: Information leak in cryptography socket NETLINK_CRYPTO call.
[1gefn4lp] CVE-2019-19965: Denial-of-service in SCSI device removal.
[6hu77eez] Invalid memory access when sending an excessively large packet using Segmentation Offloads.
[f0zxddhg] Livelock in loop device block resize operation.
[2lgm3hz9] CVE-2019-14814, CVE-2019-14815, CVE-2019-14816: Denial-of-service when parsing access point settings in Marvell WiFi-Ex driver.
[3yqxyw42] CVE-2019-20096: Memory leak while changing DCCP socket SP feature values.
[9g5kf79r] Improved fix for CVE-2020-2732: Privilege escalation in Intel KVM nested emulation.
[bq9hiiuj] Race condition in ipoib during high request load causes denial-of-service.
[3youemoz] CVE-2020-11494: Information leak in serial line CAN device communication.
[jpbi3wnm] Use-after-free when removing generic block device.
[if1ety6t] Memory corruption when reading EFI sysfs entries.
[iv8r17d8] CVE-2020-8648: Use-after-free in virtual terminal selection buffer.
[mojwd0zk] Various Spectre-V1 information leaks in KVM.
[nvi6r5wx] CVE-2019-19527: Denial-of-service in USB HID device open.
[o3df6mds] CVE-2020-8647, CVE-2020-8649: Use-after-free in the VGA text console driver.
[kjyqg48a] CVE-2019-19532: Denial-of-service when initializing HID devices.
[74j9dhee] Divide-by-zero when CPU capacity changes causes denial-of-service.
[lgsoxuy7] CVE-2019-19768: Use-after-free when reporting an IO trace.

Effective kernel version is 4.14.35-1902.302.2.el7uek

all details are there about the fixes applied by Ksplice, without any reboot.

One month later

I’ve created that on May 23th, 2020 and writing this one month later.

Here are the e-mails I’ve received from the topic subscription:

And my current machine state:

[opc@al ~]$ uptime
 19:26:39 up 38 days, 13:49,  2 users,  load average: 0.07, 0.02, 0.00
[opc@al ~]$ uname -a
Linux al 4.14.35-1902.301.1.el7uek.x86_64 #2 SMP Tue Mar 31 16:50:32 PDT 2020 x86_64 x86_64 x86_64 GNU/Linux
[opc@al ~]$ sudo uptrack-uname -a
Linux al 4.14.35-1902.303.4.1.el7uek.x86_64 #2 SMP Fri May 29 14:56:41 PDT 2020 x86_64 x86_64 x86_64 GNU/Linux
[opc@al ~]$

The VM has been running 24/7 without outage and the effective kernel is now higher than when installed.

Ksplice updates

This effective kernel has been updated on Tue Jun 16 08:04:33 GMT 2020 as reported by this e-mail I received:

noreply@notification.eu-frankfurt-1.oraclecloud.com
Jun 16, 2020, 10:04 AM
to AutonomousLinux

+------------------------------------------------------------------------+
|  Summary (Tue Jun 16 08:04:33 GMT 2020)                                |
+------------------------------------------------------------------------+
Ksplice updates installed: yes
Yum updates installed: no
Uptime: 08:04:33 up 24 days,  2:27,  0 users,  load average: 0.72, 0.20, 0.06
+------------------------------------------------------------------------+
|  Ksplice upgrade report                                                |
+------------------------------------------------------------------------+
Running 'ksplice -y all upgrade'.
Updating on-disk packages for new processes
Loaded plugins: langpacks
No packages marked for update
Nothing to do.
The following steps will be taken:
Install [i622mubr] Information leak in KVM_HC_CLOCK_PAIRING hypercall.
Install [35xnb9pi] CVE-2019-9500: Potential heap overflow in Broadcom FullMAC WLAN driver.
Install [ppqwl5uh] CVE-2019-15505: Out-of-bounds access in Technisat DVB-S/S2 USB2.0 driver.
Install [ctobm6wo] CVE-2019-19767: Use-after-free in with malformed ext4 filesystems.
Install [l5so0kqe] CVE-2019-19056, CVE-2019-19057: Denial-of-service in the Marvell mwifiex PCIe driver.
Install [b4iszmv7] CVE-2019-20636: Out-of-bounds write via crafted keycode table.
Install [5oec4s3n] Denial-of-service when mounting an ocfs2 filesystem.
Install [rafq9pe9] CVE-2019-9503: Denial-of-service when receiving firmware event frames over a Broadcom WLAN USB dongle.
Install [nlpu7kxi] Denial-of-service when initializing a serial CAN device.
Install [lnz9di5t] CVE-2020-11608: NULL pointer dereference when initializing USB GSPCA based webcams.
Install [2bodr9yk] CVE-2019-19537: Denial-of-service in USB character device registration.
Install [9iw2y1wn] CVE-2019-19524: Use-after-free when unregistering memoryless force-feedback driver.
Install [h5s7eh41] CVE-2020-11609: NULL pointer dereference when initializing STV06XX USB Camera device.
Install [behlqry8] Denial-of-service via invalid TSC values in KVM.
Install [onllaobw] CVE-2019-12819: Use-after-free during initialization of MDIO bus driver.
Install [fdn63bdc] CVE-2019-11599: Information leak in the coredump implementation.
Install [kb3b03z9] CVE-2019-19058: Denial-of-service in iwlwifi firmware interface.
Install [mgfi6p6r] Use-after-free when writing to SLIP serial line.
Install [hs2h9j8w] CVE-2019-14896, CVE-2019-14897: Denial-of-service when parsing BSS in Marvell 8xxx Libertas WLAN driver.
Install [bb9sd52m] CVE-2020-11668: NULL pointer dereference when initializing Xirlink C-It USB camera device.
Install [p4ygwgyj] Information leak in KVM's VMX operation path.
Install [1uxt1xo6] NFSv4 client fails to correctly renew lease when using fsinfo.
Install [hjoeh3zi] CVE-2020-0543: Side-channel information leak using SRBDS.
Installing [i622mubr] Information leak in KVM_HC_CLOCK_PAIRING hypercall.
Installing [35xnb9pi] CVE-2019-9500: Potential heap overflow in Broadcom FullMAC WLAN driver.
Installing [ppqwl5uh] CVE-2019-15505: Out-of-bounds access in Technisat DVB-S/S2 USB2.0 driver.
Installing [ctobm6wo] CVE-2019-19767: Use-after-free in with malformed ext4 filesystems.
Installing [l5so0kqe] CVE-2019-19056, CVE-2019-19057: Denial-of-service in the Marvell mwifiex PCIe driver.
Installing [b4iszmv7] CVE-2019-20636: Out-of-bounds write via crafted keycode table.
Installing [5oec4s3n] Denial-of-service when mounting an ocfs2 filesystem.
Installing [rafq9pe9] CVE-2019-9503: Denial-of-service when receiving firmware event frames over a Broadcom WLAN USB dongle.
Installing [nlpu7kxi] Denial-of-service when initializing a serial CAN device.
Installing [lnz9di5t] CVE-2020-11608: NULL pointer dereference when initializing USB GSPCA based webcams.
Installing [2bodr9yk] CVE-2019-19537: Denial-of-service in USB character device registration.
Installing [9iw2y1wn] CVE-2019-19524: Use-after-free when unregistering memoryless force-feedback driver.
Installing [h5s7eh41] CVE-2020-11609: NULL pointer dereference when initializing STV06XX USB Camera device.
Installing [behlqry8] Denial-of-service via invalid TSC values in KVM.
Installing [onllaobw] CVE-2019-12819: Use-after-free during initialization of MDIO bus driver.
Installing [fdn63bdc] CVE-2019-11599: Information leak in the coredump implementation.
Installing [kb3b03z9] CVE-2019-19058: Denial-of-service in iwlwifi firmware interface.
Installing [mgfi6p6r] Use-after-free when writing to SLIP serial line.
Installing [hs2h9j8w] CVE-2019-14896, CVE-2019-14897: Denial-of-service when parsing BSS in Marvell 8xxx Libertas WLAN driver.
Installing [bb9sd52m] CVE-2020-11668: NULL pointer dereference when initializing Xirlink C-It USB camera device.
Installing [p4ygwgyj] Information leak in KVM's VMX operation path.
Installing [1uxt1xo6] NFSv4 client fails to correctly renew lease when using fsinfo.
Installing [hjoeh3zi] CVE-2020-0543: Side-channel information leak using SRBDS.
Your kernel is fully up to date.
Effective kernel version is 4.14.35-1902.303.4.1.el7uek
+------------------------------------------------------------------------+
|  Yum upgrade report                                                    |
+------------------------------------------------------------------------+
Running 'yum-cron' with update cmd: default.
+------------------------------------------------------------------------+
|  Ksplice updates status                                                |
+------------------------------------------------------------------------+
Running 'ksplice all show'.
Ksplice user-space updates:
No Ksplice user-space updates installed

Ksplice kernel updates:
Installed updates:
[cp1p7rl5] Known exploit detection.
[3kfqruxl] Known exploit detection for CVE-2017-7308.
[6vy9wlov] Known exploit detection for CVE-2018-14634.
[r8wncd28] KPTI enablement for Ksplice.
[3e9je971] Known exploit detection for CVE-2018-18445.
[20bmudk6] Out-of-bounds access when classifying network packets with traffic control index.
[oy5cke5u] NULL dereference while writing Hyper-V SINT14 MSR.
[5jsm8lzj] CVE-2020-9383: Information leak in floppy disk driver.
[5p7yd05e] NULL pointer dereference when initializing Differentiated Services marker driver.
[sajmv0xh] CVE-2018-19854: Information leak in cryptography socket NETLINK_CRYPTO call.
[1gefn4lp] CVE-2019-19965: Denial-of-service in SCSI device removal.
[6hu77eez] Invalid memory access when sending an excessively large packet using Segmentation Offloads.
[f0zxddhg] Livelock in loop device block resize operation.
[2lgm3hz9] CVE-2019-14814, CVE-2019-14815, CVE-2019-14816: Denial-of-service when parsing access point settings in Marvell WiFi-Ex driver.
[3yqxyw42] CVE-2019-20096: Memory leak while changing DCCP socket SP feature values.
[9g5kf79r] Improved fix for CVE-2020-2732: Privilege escalation in Intel KVM nested emulation.
[bq9hiiuj] Race condition in ipoib during high request load causes denial-of-service.
[3youemoz] CVE-2020-11494: Information leak in serial line CAN device communication.
[jpbi3wnm] Use-after-free when removing generic block device.
[if1ety6t] Memory corruption when reading EFI sysfs entries.
[iv8r17d8] CVE-2020-8648: Use-after-free in virtual terminal selection buffer.
[mojwd0zk] Various Spectre-V1 information leaks in KVM.
[nvi6r5wx] CVE-2019-19527: Denial-of-service in USB HID device open.
[o3df6mds] CVE-2020-8647, CVE-2020-8649: Use-after-free in the VGA text console driver.
[kjyqg48a] CVE-2019-19532: Denial-of-service when initializing HID devices.
[74j9dhee] Divide-by-zero when CPU capacity changes causes denial-of-service.
[lgsoxuy7] CVE-2019-19768: Use-after-free when reporting an IO trace.
[i622mubr] Information leak in KVM_HC_CLOCK_PAIRING hypercall.
[35xnb9pi] CVE-2019-9500: Potential heap overflow in Broadcom FullMAC WLAN driver.
[ppqwl5uh] CVE-2019-15505: Out-of-bounds access in Technisat DVB-S/S2 USB2.0 driver.
[ctobm6wo] CVE-2019-19767: Use-after-free in with malformed ext4 filesystems.
[l5so0kqe] CVE-2019-19056, CVE-2019-19057: Denial-of-service in the Marvell mwifiex PCIe driver.
[b4iszmv7] CVE-2019-20636: Out-of-bounds write via crafted keycode table.
[5oec4s3n] Denial-of-service when mounting an ocfs2 filesystem.
[rafq9pe9] CVE-2019-9503: Denial-of-service when receiving firmware event frames over a Broadcom WLAN USB dongle.
[nlpu7kxi] Denial-of-service when initializing a serial CAN device.
[lnz9di5t] CVE-2020-11608: NULL pointer dereference when initializing USB GSPCA based webcams.
[2bodr9yk] CVE-2019-19537: Denial-of-service in USB character device registration.
[9iw2y1wn] CVE-2019-19524: Use-after-free when unregistering memoryless force-feedback driver.
[h5s7eh41] CVE-2020-11609: NULL pointer dereference when initializing STV06XX USB Camera device.
[behlqry8] Denial-of-service via invalid TSC values in KVM.
[onllaobw] CVE-2019-12819: Use-after-free during initialization of MDIO bus driver.
[fdn63bdc] CVE-2019-11599: Information leak in the coredump implementation.
[kb3b03z9] CVE-2019-19058: Denial-of-service in iwlwifi firmware interface.
[mgfi6p6r] Use-after-free when writing to SLIP serial line.
[hs2h9j8w] CVE-2019-14896, CVE-2019-14897: Denial-of-service when parsing BSS in Marvell 8xxx Libertas WLAN driver.
[bb9sd52m] CVE-2020-11668: NULL pointer dereference when initializing Xirlink C-It USB camera device.
[p4ygwgyj] Information leak in KVM's VMX operation path.
[1uxt1xo6] NFSv4 client fails to correctly renew lease when using fsinfo.
[hjoeh3zi] CVE-2020-0543: Side-channel information leak using SRBDS.

Effective kernel version is 4.14.35-1902.303.4.1.el7uek

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Ksplice updates

I’ve also seen a notification about failed updates:

+------------------------------------------------------------------------+
|  Summary (Mon Jun 29 08:03:19 GMT 2020)                                |
+------------------------------------------------------------------------+
Ksplice updates installed: failed
Yum updates installed: no
Uptime: 08:03:19 up 37 days,  2:25,  0 users,  load average: 0.31, 0.08, 0.03
+------------------------------------------------------------------------+
|  Ksplice upgrade report                                                |
+------------------------------------------------------------------------+
Running 'ksplice -y all upgrade'.
Updating on-disk packages for new processes
Loaded plugins: langpacks
No packages marked for update
Nothing to do.
Unexpected error communicating with the Ksplice Uptrack server. Please
check your network connection and try again. If this error re-occurs,
e-mail ksplice-support_ww@oracle.com.

(Network error: TCP connection reset by peer)

Ok, network error at that time.
However, the next run was ok:

+------------------------------------------------------------------------+
|  Summary (Tue Jun 30 08:03:13 GMT 2020)                                |
+------------------------------------------------------------------------+
Ksplice updates installed: no
Yum updates installed: no
Uptime: 08:03:13 up 38 days,  2:25,  1 user,  load average: 0.00, 0.00, 0.00

and I can confirm by running manually:

[opc@al ~]$ ksplice -y all upgrade
Error: failed to configure the logger
[opc@al ~]$ sudo ksplice -y all upgrade
Updating on-disk packages for new processes
Loaded plugins: langpacks
ol7_x86_64_userspace_ksplice                                                                                                                     | 2.8 kB  00:00:00
No packages marked for update
100% |################################################################################################################################################################|
Nothing to do.
Nothing to be done.
Your kernel is fully up to date.
Effective kernel version is 4.14.35-1902.303.4.1.el7uek

Ksplice is about the kernel and some user space libraries such as glibc and openssl.
But Autonomous Linux also updates the packages.

Yum updates

In addition to kernel patches, the packages are also updated:

The following updates will be applied on al:
================================================================================
 Package                  Arch    Version                  Repository      Size
================================================================================
Installing:
 kernel                   x86_64  3.10.0-1127.13.1.el7     al7             50 M
Updating:
 bpftool                  x86_64  3.10.0-1127.13.1.el7     al7            8.4 M
 ca-certificates          noarch  2020.2.41-70.0.el7_8     al7            382 k
 kernel-tools             x86_64  3.10.0-1127.13.1.el7     al7            8.0 M
 kernel-tools-libs        x86_64  3.10.0-1127.13.1.el7     al7            8.0 M
 libgudev1                x86_64  219-73.0.1.el7_8.8       al7            107 k
 microcode_ctl            x86_64  2:2.1-61.10.0.1.el7_8    al7            2.7 M
 ntpdate                  x86_64  4.2.6p5-29.0.1.el7_8.2   al7             86 k
 python-perf              x86_64  3.10.0-1127.13.1.el7     al7            8.0 M
 python36-oci-cli         noarch  2.12.0-1.el7             al7            4.4 M
 python36-oci-sdk         x86_64  2.17.0-1.el7             al7             10 M
 rsyslog                  x86_64  8.24.0-52.el7_8.2        al7            620 k
 selinux-policy           noarch  3.13.1-266.0.3.el7_8.1   al7            497 k
 selinux-policy-targeted  noarch  3.13.1-266.0.3.el7_8.1   al7            7.2 M
 systemd                  x86_64  219-73.0.1.el7_8.8       al7            5.1 M
 systemd-libs             x86_64  219-73.0.1.el7_8.8       al7            416 k
 systemd-python           x86_64  219-73.0.1.el7_8.8       al7            143 k
 systemd-sysv             x86_64  219-73.0.1.el7_8.8       al7             95 k
Removing:
 kernel                   x86_64  3.10.0-1127.el7          @anaconda/7.8   64 M

Transaction Summary
================================================================================
Install   1 Package
Upgrade  17 Packages
Remove    1 Package
The updates were successfully applied

All packages are maintained up-to-date without human intervention and without downtime.

Package repository

The package repository is limited:

[opc@al ~]$ yum repolist
Loaded plugins: langpacks
ol7_x86_64_userspace_ksplice/primary_db                                                                                                          | 193 kB  00:00:00
repo id                                                       repo name                                                                                           status
!al7/x86_64                                                   Autonomous Linux 7Server (x86_64)                                                                   3,392
ol7_x86_64_userspace_ksplice                                  Ksplice aware userspace packages for Oracle Linux 7Server (x86_64)                                    438
repolist: 3,830
[opc@al ~]$ yum list all | wc -l
1462

1462 packages in one repo.
As a comparison, here is an Oracle Enterprise Linux image:

[opc@ol ~]$ yum repolist
Loaded plugins: langpacks, ulninfo
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
repo id                                                  repo name                                                                                                status
!ol7_UEKR5/x86_64                                        Latest Unbreakable Enterprise Kernel Release 5 for Oracle Linux 7Server (x86_64)                            200
!ol7_addons/x86_64                                       Oracle Linux 7Server Add ons (x86_64)                                                                       421
!ol7_developer/x86_64                                    Oracle Linux 7Server Development Packages (x86_64)                                                        1,319
!ol7_developer_EPEL/x86_64                               Oracle Linux 7Server Development Packages (x86_64)                                                       31,78$
!ol7_ksplice                                             Ksplice for Oracle Linux 7Server (x86_64)                                                                 6,41$
!ol7_latest/x86_64                                       Oracle Linux 7Server Latest (x86_64)                                                                     18,86$
!ol7_oci_included/x86_64                                 Oracle Software for OCI users on Oracle Linux 7Server (x86_64)                                              26$
!ol7_optional_latest/x86_64                              Oracle Linux 7Server Optional Latest (x86_64)                                                            13,91$
!ol7_software_collections/x86_64                         Software Collection Library release 3.0 packages for Oracle Linux 7 (x86_64)                             14,47$
repolist: 87,645
[opc@ol ~]$ yum list all | wc -l
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
36720
[opc@ol ~]$

There is a lot more here. Remember that OEL is compatible with RHEL.

If you need more packages you can open a SR and ask to have it added to the Autonomous Linux repository. For example, I use tmux everyday, especially in a free tier VM (see https://blog.dbi-services.com/always-free-always-up-tmux-in-the-oracle-cloud-with-ksplice-updates/).

If you don’t want to ask for it, there’s the possibility to add public-yum-ol7.repo there:

[opc@al ~]$ sudo yum-config-manager --add-repo http://yum.oracle.com/public-yum-ol7.repo
Loaded plugins: langpacks
adding repo from: http://yum.oracle.com/public-yum-ol7.repo
grabbing file http://yum.oracle.com/public-yum-ol7.repo to /etc/yum.repos.d/public-yum-ol7.repo
repo saved to /etc/yum.repos.d/public-yum-ol7.repo

This added the public Oracle Enterprise Linux repository. Is it correct to do that? It depends what you want: the minimum validated by Oracle to be autonomously updated without any problem, or a little additional customization.

And then install the package you want:

[opc@al ~]$ sudo yum install -y tmux

Loaded plugins: langpacks
Resolving Dependencies
--> Running transaction check
---> Package tmux.x86_64 0:1.8-4.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

========================================================================================================================================================================
 Package                              Arch                                   Version                                   Repository                                  Size
========================================================================================================================================================================
Installing:
 tmux                                 x86_64                                 1.8-4.el7                                 ol7_latest                                 241 k

Transaction Summary
========================================================================================================================================================================
Install  1 Package

Total download size: 241 k
Installed size: 554 k
Downloading packages:
tmux-1.8-4.el7.x86_64.rpm                                                                                                                        | 241 kB  00:00:00
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : tmux-1.8-4.el7.x86_64                                                                                                                                1/1
  Verifying  : tmux-1.8-4.el7.x86_64                                                                                                                                1/1

Installed:
  tmux.x86_64 0:1.8-4.el7

Now the package is installed and will be updated

Autonomous cron

Those updates are scheduled by cron but you change the schedule through the al-config bash script provided:

[opc@al ~]$ sudo al-config -s
Current daily auto update time window(24-hour): 7-11
Current daily auto update time(24-hour): 08:03

This has set a random time during the 7am to 11 am window, which is here 08:03

[opc@al ~]$ cat /etc/cron.d/al-update
# Daily cron job for AL auto updates.
# Created by al-config, do not modify this file.
# If you want to change update time, use
# 'sudo al-config -w ' to set auto update time window
3 8 * * * root /usr/sbin/al-update >/dev/null

That’s the autonomous thing here: you don’t set the crontab job. You just call the al-config with a time window and it sets the crontab for you in a random time within this window.

Let’s play with this:

[opc@al ~]$ sudo al-config -w 0-2
Configured daily auto update time window(24-hour): 0-2
Configured daily auto update time(24-hour): 01:12
Created cron job file /etc/cron.d/al-update .
[opc@al ~]$ sudo al-config -w 0-2
Configured daily auto update time window(24-hour): 0-2
Configured daily auto update time(24-hour): 01:33
Created cron job file /etc/cron.d/al-update .
[opc@al ~]$ sudo al-config -w 0-2
Configured daily auto update time window(24-hour): 0-2
Configured daily auto update time(24-hour): 00:47
Created cron job file /etc/cron.d/al-update .
[opc@al ~]$ sudo al-config -w 0-2
Configured daily auto update time window(24-hour): 0-2
Configured daily auto update time(24-hour): 00:00
Created cron job file /etc/cron.d/al-update .
[opc@al ~]$ sudo al-config -w 0-2
Configured daily auto update time window(24-hour): 0-2
Configured daily auto update time(24-hour): 00:41
Created cron job file /etc/cron.d/al-update .

You see the idea. Very simple. But simple is awesome, right?

What is this scheduled job doing autonomously every day? You see it in the notification e-mail. Basically it runs:

ksplice -y all upgrade
yum-cron
ksplice all show

and sends the output to your e-mail

This is what keeps your Autonomous Linux up-to-date: ksplice, yum, and the output sent to your e-mail through:

Received: by omta-ad1-fd1-102-eu-frankfurt-1.omtaad1.vcndpfra.oraclevcn.com (Oracle Communications Messaging Server 8.1.0.1.20200619 64bit (built Jun 19 2020)) w

This is an excerpt from the notification e-mail headers. “Oracle Communications Messaging Server” is a heritage from Sun which, according to wikipedia, has its roots in Netscape Messaging Server. All those little bricks from years of enterprise IT are nicely wired together to bring this automation known as Autonomous.

Cet article Oracle Autonomous Linux: cron’d ksplice and yum updates est apparu en premier sur Blog dbi services.

When dealing with cascading or far sync in a Data Guard environment, it is important to understand how to configure the RedoRoutes property.
By default, a primary database sends redo to each transport destination that is configured in the destination. We can create more complex transport topology, depending of our environment, using the RedoRoutes property.
Basically the RedoRoutes property has this format

(redo_routing_rule_1) [(redo_routing_rule_n)]

Where each routing rule contains a redo source field and a redo destination field separated by a colon:

(redo source : redo destination)

One can have more information in Oracle documentation

In this blog I am trying to simply explain how to configure the RedoRoutes property in a Data Guard environment with Far Sync Instance. See my previous blog for far sync instance creation.

I am using Oracle 20c.

The first configuration we consider is the following one

We have
1 primary database: prod20_site1
2 standby databases: prod20_site2 and prod20_site4
1 far sync instance fs_site3

For far sync creation with Oracle 20c see my previous blog

Below the status of the broker configuration

DGMGRL> show configuration

Configuration - prod20

  Protection Mode: MaxAvailability
  Members:
  prod20_site1 - Primary database
    prod20_site2 - Physical standby database
    prod20_site4 - Physical standby database
    fs_site3     - Far sync instance

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS   (status updated 47 seconds ago)

Actually, there is no configured RedoRoutes

DGMGRL> show database prod20_site1 redoroutes;
  RedoRoutes = ''
DGMGRL> show database prod20_site2 redoroutes;
  RedoRoutes = ''
DGMGRL> show database prod20_site4 redoroutes;
  RedoRoutes = ''
DGMGRL> 

For this configuration I want the primary database to send the redo according following rules

prod20_site2 will receive redo directly from prod20_site1
prod20_site1 =====> prod20_site2

prod20_site4 will receive redo via fs_site3 which will forward redo to prod20_site4
prod20_site1 =====> fs_site3 =====> prod20_site4

and if fs_site3 is not available, prod20_site4 will receive directly redo from prod20_site1
prod20_site1 =====> prod20_site4

For this we have to first edit the primary database RedoRoutes property like

DGMGRL> edit database prod20_site1 set property redoroutes='(local:prod20_site2,(fs_site3 priority=1,prod20_site4 priority=2))';
Property "redoroutes" updated

In this rule we have these meanings

local:prod20_site2: if prod20_site1 is the primary database then redo will be sent to prod20_site2

local: (fs_site3 priority=1,prod20_site4 priority=2 ): if prod20_site1 is the primary database then redo will be sent to fs_site3 or to prod20_site4. As the priority of the fs_site3 is higher, indeed smaller priority numbers mean higher priority, redo will be sent first to fs_site3, and if fs_site3 is unavailable, changes will be sent to prod20_site4.
Just note that as fs_site3 has a higher priority, if fs_site3 becomes available, redo will be again sent to fs_site3.

And then we have to tell to fs_site3 to forward redo received from prod20_site1 to prod20_site4.

DGMGRL> edit far_sync fs_site3 set property redoroutes='(prod20_site1:prod20_site4 ASYNC)';
Property "redoroutes" updated

Below the redoroutes we have configured for prod20_site1 and fs_site3

DGMGRL> show database prod20_site1 redoroutes;
  RedoRoutes = '(local:prod20_site2,(fs_site3 priority=1,prod20_site4 priority=2))'
DGMGRL> show database prod20_site2 redoroutes;
  RedoRoutes = ''
DGMGRL> show database prod20_site4 redoroutes;
  RedoRoutes = ''
DGMGRL> show far_sync  fs_site3 redoroutes;
  RedoRoutes = '(prod20_site1:prod20_site4 ASYNC)'
DGMGRL>

And we can verify the status of our configuration

DGMGRL> show configuration verbose


Configuration - prod20

  Protection Mode: MaxPerformance
  Members:
  prod20_site1 - Primary database
    prod20_site2 - Physical standby database
    fs_site3     - Far sync instance
      prod20_site4 - Physical standby database
    prod20_site4 - Physical standby database (alternate of fs_site3)
…
…
Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS

DGMGRL>

Let’s now consider this configuration where we have two far syn instances. As in the first configuration, we want to send first the redo to far sync instances if possible, otherwise redo will be send directly to standby databases

The RedoRoutes property of the primary can be configured as below

DGMGRL> edit database prod20_site1 set property redoroutes='(local:(fs_site5 priority=1,prod20_site2 priority=2),(fs_site3 priority=1,prod20_site4 priority=2))';
Warning: ORA-16677: Standby database has the same or higher priority than other members specified in the RedoRoutes group.

Property "redoroutes" updated
DGMGRL>

And the redoroutes for the far sysnc fs_site5 can be adjusted like

DGMGRL> edit far_sync fs_site5 set property redoroutes='(prod20_site1:prod20_site2 ASYNC)';
Property "redoroutes" updated
DGMGRL>

We can then verify the satus of the configuration

DGMGRL> show configuration verbose

Configuration - prod20

  Protection Mode: MaxPerformance
  Members:
  prod20_site1 - Primary database
    fs_site5     - Far sync instance
      prod20_site2 - Physical standby database
    prod20_site2 - Physical standby database (alternate of fs_site5)
    fs_site3     - Far sync instance
      prod20_site4 - Physical standby database
    prod20_site4 - Physical standby database (alternate of fs_site3)

…
…

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS

DGMGRL>

As we can see when configuring RedoRoutes, we sometimes have to deal with the property PRIORITY.
This property can have a value between 1 and 8. 1 as the highest priority and 8 the lowest priority.
Let’s consider two destination A and B in the same group

Case 1: A and B with the same prority

Redo will be sent to A or B, let’s say A. When A is unavailable, redo will be then sent to B. And when A become reachable again, redo will continue to be sent to B.

(local:(A priority=1,B priority=1))

Case 2: A has a higher priority then B
Redo will be sent to A. If A becomes unavailable, redo will be sent to B. And if A becomes again reachable, redo will be sent to A as it has the highest priority

(local:(A priority=1,B priority=2))

But sometimes in the same group, we may want to send redo to both members. For example if we consider the following configuration, we just want that redo will be sent to fs_site3 if possible and if fs_site3 is not reachable then changes will be sent to both prod20_site2 et prod20_site4.

In this case we can use the PRIORITY 8 which has a special meaning. If the primary sends redo to a member with PRIORITY 8, then it must also send these redo to each member with the PRIORITY 8 in the group

In the configuration above, we want following rules

prod20_site1 will send changes to fs_site3 which will forward to prod20_site2 and prod20_site4 and if fs_site3 is not avalaible, prod20_site1 will ship redo to both standby databases.

And when fs_site3 becomes again available, redo will be send again to fs_site3

The redoRoutes for the primary database can be like

DGMGRL> edit database prod20_site1 set property redoroutes='(local:(fs_site3 priority=1,prod20_site2 priority=8,prod20_site4 priority=8))';
Warning: ORA-16677: Standby database has the same or higher priority than other members specified in the RedoRoutes group.

Property "redoroutes" updated
DGMGRL>

And for the far sync instance

DGMGRL> edit far_sync fs_site3 set property redoroutes='(prod20_site1:prod20_site2 ASYNC,prod20_site4 ASYNC)';
Property "redoroutes" updated
DGMGRL>

The status of the configuration

DGMGRL> show configuration verbose

Configuration - prod20

  Protection Mode: MaxPerformance
  Members:
  prod20_site1 - Primary database
    fs_site3     - Far sync instance
      prod20_site2 - Physical standby database
      prod20_site4 - Physical standby database
    prod20_site2 - Physical standby database (alternate of fs_site3)
    prod20_site4 - Physical standby database (alternate of fs_site3)
…
…

Fast-Start Failover:  Disabled

Configuration Status:
SUCCESS

DGMGRL>

Conclusion

Depending to the configuration, the redo transport topology can be very complex. What I can recommend when dealing with far sync instances, is to think about all possible cases, including switchover and failover. And based of all possible cases to design an architecture for the redo transport. In this blog we just consider the case when prod20_site1 is the primary.

Cet article Oracle Data Guard RedoRoutes : What is Priority 8 ? est apparu en premier sur Blog dbi services.

I had the opportunity to participate to POUG day 1 and wanted through this blog to share some of my feedback on the interesting sessions I could follow.

First of all, I would like to mention the great introduction done by the staff team and the great organization. POUG staff team could adapt to the coronavirus situation and organized excellent POUG virtual days. Well done!

I had the chance today to follow a few sessions :

• Developing Clusterware agents by Michal Wesolowski for which I will provide a few feedback and interesting stuff to know, later in this blog.
• The Heart of Oracle – how the core RDBMS engine works by Martin Widlake. Martin presented how the heart of oracle works from the instance to the database files going through the redo logs, archive logs. He addressed how blocks are handled, how SQL statements are parsed and optimized. By the way, did you know that during a transaction a single block goes to the SGA (buffer cache) and multiple blocks goes to the PGA, so not shared between other sessions? Same for full table scan. I did not, I was always thinking that all blocks went from the data files to the buffer cache. Also it is good to know that oracle use hashing algorithm to find a block in the SGA.
• The foundations of understanding Execution Plans by Jonathan Lewis. Great subject! Using concrete examples, Jonathan covered a complex subject : how does an execution plans work.
• Wait Events and DB time by Franck Pachot. My collegue Franck gave a very interesting session explaining wait events and DB time for which I will provide some of the information provided later in this blog.
• Analysis of a Couple AWR Reports by Toon Koppelaars. This presentation was a good follow up of Franck’s session. Toon explained how to interpret AWR Report.

Developing Clusterware agents

Michal did a great interactive presentation and demo, having the demos refreshing diagrams displayed in the presentation using webservices development. If you have the opportunity to follow one day one of Michal’s presentation, I would really encourage you to do so. You will enjoy and have fun!

We got a great introduction and explanation on how Clusters are working. From the free solution (clusterware) to payable solution (veritas cluster).

Comparison on some solutions can be found on the next picture :

Grid infrastructure is composed of :

• Clusterware / Oracle restart
• ASM

The cluster architecture looks like :

Oracle clusterware : database and clustering

We can use oracle clusterware to make high available application with built-in agents.

The command crsctl status type will provide the configuration information of one or more particular resource types. All prefixes ora are Oracle objects.

To create HA applications, cluster_resource or local_resource should be used.

Oracle tools to deal with clusterware :

• srvctl : dedicated to ora. resources, to be used form oracle_home and not GI home
• crsctl : to be used for custom resources, for monitoring all resources, managing OHAS resources, managing CRS itself (crsctl stop/start crs)

Oracle Grid Infrastructures standalone Agents :
HA agents for oracle applications like GoldenGate, peoplesoft, weblogic, mysql, …. Written in Perl, easy to install and manage.

Standard Edition HA :

• Available from GI 19.7 and DB SE2 19.7
• No HA/GI for SE2 from 19.3 to 19.6
• Need ASM or ACFS

As seen in the next picture, we can understand that clusterware is more complex that we could imagine :

Dependencies between ressources (node 1 -> RES A -> RESB):
To display dependency tree we will use crsctl stat res -dependency [-stop | -pullup].
To force to stop resource and all dependencies : crsctl stop res resA -f.
To start resB and automatically resA first : crsctl start res resB.
To relocate the whole chain on new node : crsctl relocate res resA -n node3 -f.
With hard dependency : both resources should be started on same node.
Pullup dependency is very important and needs to be used when having hard dependency : If resource B depends on resource A and resource A fails and then recovers, then resource B is restarted.

Resource states / return codes are displayed on next picture :

Wait Events and DB time

Wait events have been implemented since 1992 to see where the time is spent when DB is busy, to verify resource utilization, to know load profile, to see which wait can scale or not. Otherwise, without wait events tuning might be done with blinded eyes.

System calls are wait events.

Wait events can be seen in sql_trace, v$ views, statspatck, ASH, AWR, or any other tool like tkprof…

Between the fetch() and resultset, database needs to do some work : CPU work, read blocks,… Between CPU work the server process is just waiting (idle, I/O,…). Idea is then to instrument this time and do profiling.

Idle is a system call as well, waiting for network. Between fetch() and resultset it is user response time. Tuning will try to reduce this response time.

DB time (session is active) = user response time = cpu and/or wait events

Wait events can be SQL net message to client or from client, PL/SQL lock timer.

cpu time = parse queries, read blocks or sort rows.

• Tuning idea, investigate execution plans.
• Reduce parse queries : use bind variables for similar queries.
• Reduce read blocks : Use indexes for better selectivity for the predicates or use hash join to join many rows.
• Reduce sort row : Do not selet all columns (select *) if not needed.

wait events :
Only count wait events for DB time on foreground sessions. Other processes wait event can be troubleshoot further if needed.

I/O from user session process to shared buffer cache are named db file and the one to PGA are named direct path :

• db file read
• read one block to buffer cache : db file sequential read
• read multiple blocks to buffer cache : db file scattered read, db file parallel read
• db file sequential read
• single block read. waits is the throughtput of single block reads (divided by elapsed time for IOPS). wait average time is the latency to read 8k.
• physical reads si the number of blocks, physical IO request is the number of IO calls

For average time : look at the storage, get faster disk nvme, …
If count is too high : better execution plan, larger buffer cache or PGA, …

ASH viewer can be downloaded if no diagnostic license.

application wait class : locks

log file sync = commit wait

• average time is too high : reduce queue length, get faster disks
• count is too high : avoid row by row commit, use no logging operation, look at nowait

system I/O comes in major cases from background processes, backups running, contention on control file write (due to multiplexing), too many log switches

Tools : SQL trace, tkprof, v$ views

Following picture is a nice conclusion to summary wait events. I like it…

Conclusion

This POUG event was a really great event and I would encourage anybody to participate to the next one. Sessions were really interesting with high technical level. Been busy tomorrow I will unfortunately not be able to participate to day 2. Thanks POUG staff team to organize this event! Well done!

Cet article POUG 2020 Workshop Day 1 est apparu en premier sur Blog dbi services.

As we moved to Teams at dbi and one of our customers, automating tasks was a strong need.
One of the tasks that could be automated is the creation of tasks in Microsoft Planner which does not support recurring tasks. Every 4 weeks, we are patching the environment. For everyone awareness and follow up, we need to publish these dates in the planning. As the pace of these tasks is known, it is a bit repetitive to create these tasks manually.

Microsoft Power Automate (previously known as Flow) is powerful tool to automate tasks and it integrate natively with Teams. My idea was to create 4 tasks just by providing the first date and then creating all of them on a 7 days interval.

Flows Overview

1. Initialize indice to 1. We will use it to iterate
2. Initialize a First Day of Cycle object based on user input
3. Initialize an ArrayOfEnv which will be used for naming each task. For example, array can contain:
   1. Sandbox
   2. Dev
   3. Test
   4. Prod
4. Then create a loop and iterate until we reach 4
   1. Creation of the task with
      • Title based on ArrayOfEnv[indice] content
      • Date based on selected First Day of Cycle + 7 x indice
   2. Increment indice

That’s it! very basic, but can save time.

Formulas

One of the main difficulties was to find documentation on formulas that work.
For example, the date selected will be formatted with a specific format, but AddDays function do not support it well if you don’t provide expected output format. Solution is to force formatting of the date selected and have it the same across whole flow.

Main functions used for this flow:

• To get value of a variable, I used variables function with variable name as parameter.
• Add to obviously sum up all parameters provided.
• Mul to multiply.
• Creation of an array with createArray and the name I would like for each task:
  createArray('Sandbox','Dev','Test','Prod')

Flows Details

First part of it is the manual trigger with date as input:

Second part is initialization of variables:

Finally, the loop:

Formulas:

• Title:
  concat(variables('ArrayOfEnv')[variables('Indice')],' ',' Patching')
• Start and end date Time:
  addDays(variables('SelectedDate'),mul(variables('indice'),7),'yyyy-MM-dd')

Next Steps

For now, it is only a manual trigger of the flow. Next step would be to schedule that at each cycle beginning.

Power Automate looks like a promising tool, but Microsoft must work more on it to be able to have a full text mode as mix of click and formulas makes it impossible to export.

Cet article Microsoft Teams, Power Automate and Planner est apparu en premier sur Blog dbi services.

By Franck Pachot

.
This is a demo about Oracle ACFS snapshots, and how to understand the used and free space, as displayed by “df”, when there are modifications in the base parent or the snapshot children. The important concept to understand is that, when you take a snapshot, any modification to the child or parent will

[grid@cloud ~]$ asmcmd lsdg DATAC1

State    Type  Rebal  Sector  Logical_Sector  Block       AU   Total_MB    Free_MB  Req_mir_free_MB  Usable_file_MB  Offline_disks  Voting_files  Name
MOUNTED  HIGH  N         512             512   4096  4194304  214991104  191881152         11943936        59979016              0             Y  DATAC1/

On a database machine in the Oracle Cloud I have a diskgroup with lot of free space. I’ll use this DATAC1 diskgroup to store my ACFS filesystem. the size in MegaByte is not easy to read.
I can have a friendly overview from acfsutil with human readable sizes (in TeraByte there).

[grid@cloud ~]$ acfsutil info storage -u TB -l DATAC1

Diskgroup: DATAC1 (83% free)
  total disk space:         205.03
  ASM file space:            22.04
  total free space:         182.99
  net free with mirroring:   60.99
  usable after reservation:  57.20
  redundancy type:          HIGH

    Total space used by ASM non-volume files:
      used:                     19.03
      mirror used:               6.34

    volume: /dev/asm/dump-19
      total:                     1.00
      free:                      0.22
      redundancy type:         high
      file system:             /u03/dump
----
unit of measurement: TB

There’s already a volume here (/dev/asm/dump-19) which is named ‘DUMP’ and mounted as an ACFS filesystem (/u03/dump) but I’ll create a now one for this demo and will remove.

Logical volume: asmcmd volcreate

I have a diskgroup which exposes disk space to ASM. The first thing to do, in order to build a filesystem on it, is to create a logical volume, which is called ADVM for “ASM Dynamic Volume Manager”.

[grid@cloud ~]$ asmcmd volcreate -G DATAC1 -s 100G MYADVM

I’m creating a 100GB new volume, identified by its name (MYADVM) within the diskgroup (DATAC1). The output is not verbose at all but I can check it with volinfo.

[grid@cloud ~]$ asmcmd volinfo -G DATAC1 -a

Diskgroup Name: DATAC1

         Volume Name: DUMP
         Volume Device: /dev/asm/dump-19
         State: ENABLED
         Size (MB): 1048576
         Resize Unit (MB): 512
         Redundancy: HIGH
         Stripe Columns: 8
         Stripe Width (K): 1024
         Usage: ACFS
         Mountpath: /u03/dump

         Volume Name: MYADVM
         Volume Device: /dev/asm/myadvm-19
         State: ENABLED
         Size (MB): 102400
         Resize Unit (MB): 512
         Redundancy: HIGH
         Stripe Columns: 8
         Stripe Width (K): 1024
         Usage:
         Mountpath:

With “-a” I show all volumes on the diskgroup, but I could have mentioned the volume name. This is what we will do later.

“Usage” is empty because there’s no filesystem created yet, and “Mountpath” is empty because it is not mounted. The information I need is the Volume Device (/dev/asm/myadvm-19) as I’ll have access to it from the OS.

[grid@cloud ~]$ lsblk -a /dev/asm/myadvm-19

NAME          MAJ:MIN  RM  SIZE RO TYPE MOUNTPOINT
asm!myadvm-19 248:9731  0  100G  0 disk

[grid@cloud ~]$ lsblk -t /dev/asm/myadvm-19

NAME          ALIGNMENT MIN-IO OPT-IO PHY-SEC LOG-SEC ROTA SCHED    RQ-SIZE   RA
asm!myadvm-19         0    512      0     512     512    1 deadline     128  128

[grid@cloud ~]$ fdisk -l /dev/asm/myadvm-19

Disk /dev/asm/myadvm-19: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Visible from the OS, I have a 100GB volume with nothing there: I need to format it.

Filesystem: Linux mkfs

[grid@cloud ~]$ grep -v nodev /proc/filesystems

        iso9660
        ext4
        fuseblk
        acfs

ACFS is a filesystem supported by the kernel. I can use “mkfs” to format the volume to ACFS.

[grid@cloud ~]$ mkfs.acfs -f /dev/asm/myadvm-19

mkfs.acfs: version                   = 18.0.0.0.0
mkfs.acfs: on-disk version           = 46.0
mkfs.acfs: volume                    = /dev/asm/myadvm-19
mkfs.acfs: volume size               = 107374182400  ( 100.00 GB )
mkfs.acfs: Format complete.

I used “-f” because my volume was already formatted from a previous test. I have now a 100GB filesystem on this volume.

[grid@cloud ~]$ asmcmd volinfo -G DATAC1 MYADVM

Diskgroup Name: DATAC1

         Volume Name: MYADVM
         Volume Device: /dev/asm/myadvm-19
         State: ENABLED
         Size (MB): 102400
         Resize Unit (MB): 512
         Redundancy: HIGH
         Stripe Columns: 8
         Stripe Width (K): 1024
         Usage: ACFS
         Mountpath:

The “Usage” shows that ASM knows that the ADVM volume holds an ACFS filesystem.

[opc@cloud ~]$ sudo mkdir -p /myacfs

I’ll mount this filesystem to /myacfs

[opc@cloud ~]$ sudo mount -t acfs /dev/asm/myadvm-19 /myacfs

[opc@cloud ~]$ mount | grep /myacfs

/dev/asm/myadvm-19 on /myacfs type acfs (rw)

[opc@cloud ~]$ df -Th /myacfs

Filesystem         Type  Size  Used Avail Use% Mounted on
/dev/asm/myadvm-19 acfs  100G  448M  100G   1% /myacfs

[opc@cloud ~]$ ls -alrt /myacfs

total 100
drwxr-xr-x 30 root root  4096 Jun 23 10:40 ..
drwxr-xr-x  4 root root 32768 Jun 23 15:48 .
drwx------  2 root root 65536 Jun 23 15:48 lost+found

[opc@cloud ~]$ sudo umount /myacfs

I wanted to show that you can mount it from the OS but, as we have Grid Infrastructure, we usually want to manage it as a cluster resource.

[opc@cloud ~]$ sudo acfsutil registry -a /dev/asm/myadvm-19 /myacfs -u grid

acfsutil registry: mount point /myacfs successfully added to Oracle Registry

[opc@cloud ~]$ ls -alrt /myacfs

total 100
drwxr-xr-x 30 root root      4096 Jun 23 10:40 ..
drwxr-xr-x  4 grid oinstall 32768 Jun 23 15:48 .
drwx------  2 root root     65536 Jun 23 15:48 lost+found

The difference here is that I’ve set the owner of the filesystem to “grid” as that’s the user I’ll use for the demo.

Used and free space

[grid@cloud ~]$ asmcmd volinfo -G DATAC1 MYADVM

Diskgroup Name: DATAC1

         Volume Name: MYADVM
         Volume Device: /dev/asm/myadvm-19
         State: ENABLED
         Size (MB): 102400
         Resize Unit (MB): 512
         Redundancy: HIGH
         Stripe Columns: 8
         Stripe Width (K): 1024
         Usage: ACFS
         Mountpath: /myacfs

ADVM has the information about the mount path but now to interact with it I’ll use “acfsutil” for ACFS features or the standard Linux commands on filesystems.

[grid@cloud ~]$ du -ah /myacfs

64K     /myacfs/lost+found
96K     /myacfs

I have no files there: only 96 KB used.

[grid@cloud ~]$ df -Th /myacfs

Filesystem         Type  Size  Used Avail Use% Mounted on
/dev/asm/myadvm-19 acfs  100G  688M  100G   1% /myacfs

the whole size of 100GB is available.

[grid@cloud ~]$ acfsutil info storage -u GB -l DATAC1

Diskgroup: DATAC1 (83% free)
  total disk space:         209952.25
  ASM file space:           22864.75
  total free space:         187083.87
  net free with mirroring:  62361.29
  usable after reservation: 58473.23
  redundancy type:          HIGH

    Total space used by ASM non-volume files:
      used:                    19488.04
      mirror used:             6496.01

    volume: /dev/asm/myadvm-19
      total:                   100.00
      free:                     99.33
      redundancy type:         high
      file system:             /myacfs
...
----
unit of measurement: GB

“acfs info storage” shows all volumes in the diskgroup (I removed the output for the ‘DUMP’ one here)

[grid@cloud ~]$ acfsutil info fs /myacfs
/myacfs
    ACFS Version: 18.0.0.0.0
    on-disk version:       47.0
    compatible.advm:       18.0.0.0.0
    ACFS compatibility:    18.0.0.0.0
    flags:        MountPoint,Available
    mount time:   Tue Jun 23 15:52:35 2020
    mount sequence number: 8
    allocation unit:       4096
    metadata block size:   4096
    volumes:      1
    total size:   107374182400  ( 100.00 GB )
    total free:   106652823552  (  99.33 GB )
    file entry table allocation: 393216
    primary volume: /dev/asm/myadvm-19
        label:
        state:                 Available
        major, minor:          248, 9731
        logical sector size:   512
        size:                  107374182400  ( 100.00 GB )
        free:                  106652823552  (  99.33 GB )
        metadata read I/O count:         1203
        metadata write I/O count:        10
        total metadata bytes read:       4927488  (   4.70 MB )
        total metadata bytes written:    40960  (  40.00 KB )
        ADVM diskgroup:        DATAC1
        ADVM resize increment: 536870912
        ADVM redundancy:       high
        ADVM stripe columns:   8
        ADVM stripe width:     1048576
    number of snapshots:  0
    snapshot space usage: 0  ( 0.00 )
    replication status: DISABLED
    compression status: DISABLED

“acfsutil info fs” is the best way to have all information and here it shows the same as what we see from the OS: size=100GB and free=99.33GB

Add a file

[grid@cloud ~]$ dd of=/myacfs/file.tmp if=/dev/zero bs=1G count=42

42+0 records in
42+0 records out
45097156608 bytes (45 GB) copied, 157.281 s, 287 MB/s

I have created a 42 GB file in my filesystem. And now will compare the size info.

[grid@cloud ~]$ du -ah /myacfs

64K     /myacfs/lost+found
43G     /myacfs/file.tmp
43G     /myacfs

I see one additional file with 43GB

[grid@cloud ~]$ df -Th /myacfs

Filesystem         Type  Size  Used Avail Use% Mounted on
/dev/asm/myadvm-19 acfs  100G   43G   58G  43% /myacfs

The used space that was 688 MB is now 43GB, the free space which was 100 GB is now 58 GB and the 1% usage is now 43% – this is the exact math (rounded to next GB) as my file had to allocate extents for all its data.

[grid@cloud ~]$ acfsutil info storage -u GB -l DATAC1

Diskgroup: DATAC1 (83% free)
  total disk space:         209952.25
  ASM file space:           22864.75
  total free space:         187083.87
  net free with mirroring:  62361.29
  usable after reservation: 58473.23
  redundancy type:          HIGH

    Total space used by ASM non-volume files:
      used:                    19488.04
      mirror used:             6496.01

    volume: /dev/asm/myadvm-19
      total:                   100.00
      free:                     57.29
      redundancy type:         high
      file system:             /myacfs

Here the “free:” that was 99.33 GB before is now 57.29 GB which matches what we see from df.
total free: 106652823552 ( 99.33 GB )

[grid@cloud ~]$ acfsutil info fs /myacfs

/myacfs
    ACFS Version: 18.0.0.0.0
    on-disk version:       47.0
    compatible.advm:       18.0.0.0.0
    ACFS compatibility:    18.0.0.0.0
    flags:        MountPoint,Available
    mount time:   Tue Jun 23 15:52:35 2020
    mount sequence number: 8
    allocation unit:       4096
    metadata block size:   4096
    volumes:      1
    total size:   107374182400  ( 100.00 GB )
    total free:   61513723904  (  57.29 GB )
    file entry table allocation: 393216
    primary volume: /dev/asm/myadvm-19
        label:
        state:                 Available
        major, minor:          248, 9731
        logical sector size:   512
        size:                  107374182400  ( 100.00 GB )
        free:                  61513723904  (  57.29 GB )
        metadata read I/O count:         1686
        metadata write I/O count:        130
        total metadata bytes read:       8687616  (   8.29 MB )
        total metadata bytes written:    3555328  (   3.39 MB )
        ADVM diskgroup:        DATAC1
        ADVM resize increment: 536870912
        ADVM redundancy:       high
        ADVM stripe columns:   8
        ADVM stripe width:     1048576
    number of snapshots:  0
    snapshot space usage: 0  ( 0.00 )
    replication status: DISABLED
    compression status: DISABLED

What has changed here is only the “total free:” from 99.33 GB to 57.29 GB

Create a snapshot

For the moment, with no snapshot and no compression, the size allocated in the filesystem (as the “df” used) is the same as the size of the files (as the “du” file size).

[grid@cloud ~]$ acfsutil snap info /myacfs

    number of snapshots:  0
    snapshot space usage: 0  ( 0.00 )

The “acfsutil info fs” shows no snapshots, and “acfsutil snap info” shows the same but will give more details where I’ll have created snapshots.

[grid@cloud ~]$ acfsutil snap create -w S1 /myacfs

acfsutil snap create: Snapshot operation is complete.

This has created a read-write snapshot of the filesystem.

[grid@cloud ~]$ du -ah /myacfs

64K     /myacfs/lost+found
43G     /myacfs/file.tmp
43G     /myacfs

Nothing different here as this shows only the base. The snapshots are in a hidden .ACFS that is not listed but can be accessed when mentioning the path.

[grid@cloud ~]$ du -ah /myacfs/.ACFS

32K     /myacfs/.ACFS/.fileid
32K     /myacfs/.ACFS/repl
43G     /myacfs/.ACFS/snaps/S1/file.tmp
43G     /myacfs/.ACFS/snaps/S1
43G     /myacfs/.ACFS/snaps
43G     /myacfs/.ACFS

Here I see my 42 GB file in the snapshot. But, as I did no modifications there, it shares the same extents on disk. This means that even if I see two files of 42 GB there is only 42 GB allocated for those two virtual copies.

[grid@cloud ~]$ df -Th /myacfs

Filesystem         Type  Size  Used Avail Use% Mounted on

/dev/asm/myadvm-19 acfs  100G   43G   58G  43% /myacfs

As there are no additional extents allocated for this snapshot, “df” shows the same as before. Here we start to see a difference between the physical “df” size and the virtual “du” size.

[grid@cloud ~]$ acfsutil info storage -u GB -l DATAC1

Diskgroup: DATAC1 (83% free)
  total disk space:         209952.25
  ASM file space:           22864.75
  total free space:         187083.87
  net free with mirroring:  62361.29
  usable after reservation: 58473.23
  redundancy type:          HIGH

    Total space used by ASM non-volume files:
      used:                    19488.04
      mirror used:             6496.01

    volume: /dev/asm/myadvm-19
      total:                   100.00
      free:                     57.29
      redundancy type:         high
      file system:             /myacfs
        snapshot: S1 (/myacfs/.ACFS/snaps/S1)
          used:          0.00
          quota limit:   none
...
----
unit of measurement: GB

Here I have additional information for my snapshot: “snapshot: S1 (/myacfs/.ACFS/snaps/S1)” with 0 GB used because I did not modify anything in the snapshot yet. The volume still has the same free space.

[grid@cloud ~]$ acfsutil snap info /myacfs
    number of snapshots:  1
    snapshot space usage: 393216  ( 384.00 KB )

The new thing here is “number of snapshots: 1” with nearly no space usage (384 KB)

[grid@cloud ~]$ acfsutil info fs /myacfs
/myacfs
    ACFS Version: 18.0.0.0.0
    on-disk version:       47.0
    compatible.advm:       18.0.0.0.0
    ACFS compatibility:    18.0.0.0.0
    flags:        MountPoint,Available
    mount time:   Tue Jun 23 15:52:35 2020
    mount sequence number: 8
    allocation unit:       4096
    metadata block size:   4096
    volumes:      1
    total size:   107374182400  ( 100.00 GB )
    total free:   61513723904  (  57.29 GB )
    file entry table allocation: 393216
    primary volume: /dev/asm/myadvm-19
        label:
        state:                 Available
        major, minor:          248, 9731
        logical sector size:   512
        size:                  107374182400  ( 100.00 GB )
        free:                  61513723904  (  57.29 GB )
        metadata read I/O count:         4492
        metadata write I/O count:        236
        total metadata bytes read:       24363008  (  23.23 MB )
        total metadata bytes written:    12165120  (  11.60 MB )
        ADVM diskgroup:        DATAC1
        ADVM resize increment: 536870912
        ADVM redundancy:       high
        ADVM stripe columns:   8
        ADVM stripe width:     1048576
    number of snapshots:  1
    snapshot space usage: 393216  ( 384.00 KB )
    replication status: DISABLED
    compression status: DISABLED

Here I have more detail: those 384 KB are for the file allocation table only.

Write on snapshot

My snapshot shows no additional space but that will not stay as the goal is to do some modifications, within the same file, like a database would do on its datafiles as soon as it is opened read-write.

[grid@cloud ~]$ dd of=/myacfs/.ACFS/snaps/S1/file.tmp if=/dev/zero bs=1G count=10 conv=notrunc

10+0 records in
10+0 records out
10737418240 bytes (11 GB) copied, 58.2101 s, 184 MB/s

I’ve overwritten 10GB within the 42 GB file but the remaining 32 are still the same (that’s what the conv=notrunc is doing – not truncating the end of file).

[grid@cloud ~]$ du -ah /myacfs

64K     /myacfs/lost+found
43G     /myacfs/file.tmp
43G     /myacfs

Nothing has changed at the base level because I modified only the file in the snapshot.

[grid@cloud ~]$ du -ah /myacfs/.ACFS

32K     /myacfs/.ACFS/.fileid
32K     /myacfs/.ACFS/repl
43G     /myacfs/.ACFS/snaps/S1/file.tmp
43G     /myacfs/.ACFS/snaps/S1
43G     /myacfs/.ACFS/snaps
43G     /myacfs/.ACFS

Nothing has changed either in the snapshot because the file is still the same size.

[grid@cloud ~]$ df -Th /myacfs

Filesystem         Type  Size  Used Avail Use% Mounted on
/dev/asm/myadvm-19 acfs  100G   53G   48G  53% /myacfs

The filesystem, has increased by the amount I modified in the snapshot: I had 58GB available and now only 48GB. Because the 10GB of extents that were shared between the shanpshot child and the base (the snapshot parent) are not the same anymore and new extents had to be allocated for the snapshot. This is similar to copy-on-write.

That’s the main point of this blog post: you don’t see this new allocation with “ls” or “du” but only with “df” or the filesystem specific tools.

[grid@cloud ~]$ acfsutil info storage -u GB -l DATAC1

Diskgroup: DATAC1 (83% free)
  total disk space:         209952.25
  ASM file space:           22864.75
  total free space:         187083.87
  net free with mirroring:  62361.29
  usable after reservation: 58473.23
  redundancy type:          HIGH

    Total space used by ASM non-volume files:
      used:                    19488.04
      mirror used:             6496.01

    volume: /dev/asm/myadvm-19
      total:                   100.00
      free:                     47.09
      redundancy type:         high
      file system:             /myacfs
        snapshot: S1 (/myacfs/.ACFS/snaps/S1)
          used:         10.10
          quota limit:   none

----
unit of measurement: GB

the volume free space has decreased fro 57.29 to 47.09 GB

[grid@cloud ~]$ acfsutil snap info /myacfs
snapshot name:               S1
snapshot location:           /myacfs/.ACFS/snaps/S1
RO snapshot or RW snapshot:  RW
parent name:                 /myacfs
snapshot creation time:      Fri Jul  3 08:01:52 2020
file entry table allocation: 393216   ( 384.00 KB )
storage added to snapshot:   10846875648   (  10.10 GB )

    number of snapshots:  1
    snapshot space usage: 10846875648  (  10.10 GB )

10 GB has been added to the snapshot for the extents that are different than the parent.

[grid@cloud ~]$ acfsutil info fs /myacfs

/myacfs
    ACFS Version: 18.0.0.0.0
    on-disk version:       47.0
    compatible.advm:       18.0.0.0.0
    ACFS compatibility:    18.0.0.0.0
    flags:        MountPoint,Available
    mount time:   Fri Jul  3 07:33:19 2020
    mount sequence number: 6
    allocation unit:       4096
    metadata block size:   4096
    volumes:      1
    total size:   107374182400  ( 100.00 GB )
    total free:   50566590464  (  47.09 GB )
    file entry table allocation: 393216
    primary volume: /dev/asm/myadvm-19
        label:
        state:                 Available
        major, minor:          248, 9731
        logical sector size:   512
        size:                  107374182400  ( 100.00 GB )
        free:                  50566590464  (  47.09 GB )
        metadata read I/O count:         9447
        metadata write I/O count:        1030
        total metadata bytes read:       82587648  (  78.76 MB )
        total metadata bytes written:    89440256  (  85.30 MB )
        ADVM diskgroup:        DATAC1
        ADVM resize increment: 536870912
        ADVM redundancy:       high
        ADVM stripe columns:   8
        ADVM stripe width:     1048576
    number of snapshots:  1
    snapshot space usage: 10846875648  (  10.10 GB )
    replication status: DISABLED

The file entry table allocation has not changed. It was pointing to the parent for all extents before. Now, 10GB of extents are pointing to the snapshot child ones.

Write on parent

If I overwrite a different part on the parent, it will need to allocate new extents as those extents are share with the snapshot.

[grid@cloud ~]$ dd of=/myacfs/file.tmp if=/dev/zero bs=1G count=10 conv=notrunc seek=20

10+0 records in
10+0 records out
10737418240 bytes (11 GB) copied, 35.938 s, 299 MB/s

this has written 10GB again, but at the 20GB offset, not overlapping the range of extents modified in the snapshot.

[grid@cloud ~]$ df -Th /myacfs
Filesystem         Type  Size  Used Avail Use% Mounted on
/dev/asm/myadvm-19 acfs  100G   63G   38G  63% /myacfs

Obviously 10GB had to be allocated for those new extents.

[grid@cloud ~]$ acfsutil snap info /myacfs
snapshot name:               S1
snapshot location:           /myacfs/.ACFS/snaps/S1
RO snapshot or RW snapshot:  RW
parent name:                 /myacfs
snapshot creation time:      Fri Jul  3 09:17:10 2020
file entry table allocation: 393216   ( 384.00 KB )
storage added to snapshot:   10846875648   (  10.10 GB )


    number of snapshots:  1
    snapshot space usage: 21718523904  (  20.23 GB )

Those 10GB modified on the base are allocated for the snapshot, because what was a pointer to the parent is now a copy of extents in the state they were before the write.

I’m not going into details of copy-on-write or redirect-on-write. You can see that at file level with “acfsutil info file” and Ludovico Caldara made a great demo of it a few years ago:

Now what happens if I modify, in the parent, the same extents that have been modified in the snapshot? I don’t need a copy of the previous version of them, right?

[grid@cloud ~]$ dd of=/myacfs/file.tmp if=/dev/zero bs=1G count=10 conv=notrunc

10+0 records in
10+0 records out
10737418240 bytes (11 GB) copied, 34.9208 s, 307 MB/s

The first 10GB of this file, since the snapshot was taken, have now been modified in the base and in all snapshots (only one here).

[grid@cloud ~]$ df -Th /myacfs
Filesystem         Type  Size  Used Avail Use% Mounted on
/dev/asm/myadvm-19 acfs  100G   74G   27G  74% /myacfs

I had 10GB allocated again for this.

[grid@cloud ~]$ acfsutil snap info /myacfs
snapshot name:               S1
snapshot location:           /myacfs/.ACFS/snaps/S1
RO snapshot or RW snapshot:  RW
parent name:                 /myacfs
snapshot creation time:      Fri Jul  3 09:17:10 2020
file entry table allocation: 393216   ( 384.00 KB )
storage added to snapshot:   10846875648   (  10.10 GB )

    number of snapshots:  1
    snapshot space usage: 32564994048  (  30.33 GB )

[grid@cloud ~]$ acfsutil info file /myacfs/.ACFS/snaps/S1/file.tmp -u |
                awk '/(Yes|No)$/{ if ( $7!=l ) o=$1 ; s[o]=s[o]+$2 ; i[o]=$7 ; l=$7} END{ for (o in s) printf "offset: %4dGB size: %4dGB Inherited: %3s\n",o/1024/1024/1024,s[o]/1024/1024/1024,i[o]}' | sort
offset:    0GB size:   10GB Inherited:  No
offset:   10GB size:   31GB Inherited: Yes

I have aggregated, with awk, the range of snapshot extents that are inherited from the parent. The first 10GB are those that I modified in the snapshot. The others, above 10GB are from the S1 snapshot.

[grid@cloud ~]$ acfsutil info file /myacfs/file.tmp -u | 
                awk '/(Yes|No)$/{ if ( $7!=l ) o=$1 ; s[o]=s[o]+$2 ; i[o]=$7 ; l=$7} END{ for (o in s) printf "offset: %4dGB size: %4dGB Inherited: %3s %s\n",o/1024/1024/1024,s[o]/1024/1024/1024,i[o],x[o]}' | sort
offset:    0GB size:   10GB Inherited:  No
offset:   10GB size:    9GB Inherited: Yes
offset:   19GB size:   10GB Inherited:  No
offset:   30GB size:   11GB Inherited: Yes

Here in the base snapshot I see as inherited, between parent and child, the two ranges that I modified: 10GB from offset 0GB and 10 GB from offset 20GB

That’s the important point: when you take a snapshot, the modifications on the parent, as well as the modifications in the snapshot, will allocate new extents to add to the snapshot.

Why is this important?

This explains why, on ODA, all non-CDB databases are created on a snapshot that has been taken when the filesystem was empty.

Read-write snapshots are really cool, especially with multitenant as they are automated with the CRATE PLUGGABLE DATABASE … SNAPSHOT COPY. But you must keep in mind that the snapshot is made at filesystem level (this may change in 20c with File-Based Snapshots). Any change to the master will allocate space, whether used or not in the snapshot copy.

I blogged about that in the past: https://blog.dbi-services.com/multitenant-thin-provisioning-pdb-snapshots-on-acfs/

Here I just wanted to clarify what you see with “ls” and “du” vs. “df” or “acfsutil info”. “ls” and “du” show the virtual size of the files. “df” shows the extents allocated in the filesystem as base extents or snapshot copies. “acfsutil info” shows those extents allocated as “storage added to snapshot” whether they were allocated for modifications on the parent or child.

[grid@cloud ~]$ acfsutil info file /myacfs/.ACFS/snaps/S1/file.tmp -u
/myacfs/.ACFS/snaps/S1/file.tmp

    flags:        File
    inode:        18014398509482026
    owner:        grid
    group:        oinstall
    size:         45097156608  (  42.00 GB )
    allocated:    45105545216  (  42.01 GB )
    hardlinks:    1
    device index: 1
    major, minor: 248,9731
    create time:  Fri Jul  3 07:36:45 2020
    access time:  Fri Jul  3 07:36:45 2020
    modify time:  Fri Jul  3 09:18:25 2020
    change time:  Fri Jul  3 09:18:25 2020
    extents:
        -----offset ----length | -dev --------offset | inherited
                  0  109051904 |    1    67511517184 | No
          109051904  134217728 |    1    67620569088 | No
          243269632  134217728 |    1    67754786816 | No
          377487360  134217728 |    1    67889004544 | No
          511705088  134217728 |    1    68023222272 | No
          645922816  134217728 |    1    68157440000 | No
          780140544  134217728 |    1    68291657728 | No
          914358272  134217728 |    1    68425875456 | No
         1048576000  134217728 |    1    68560093184 | No
         1182793728  134217728 |    1    68694310912 | No
...

The difference between “du” and “df”, which is also the “storage added to snapshot” displayed by “acfsutil snap info”, is what you see as “inherited”=No in “acfsutil info file -u” on all files, parent and child. Note that I didn’t use compression here, which is another reason for the difference between “du” and “df”.

Cet article Oracle ACFS: “du” vs. “df” and “acfsutil info” est apparu en premier sur Blog dbi services.

One of the best practices while doing upgrade of Documentum is to unlock the various repository objects before starting. This will make sure that if the upgrade process requires an update of some objects, then it will succeed and not cause you issues because you are missing some pieces. This also brings a second benefit: it means that if you ever see locked objects after the upgrade, then something probably went wrong somewhere.

In a recent upgrade, I just had this case so it was the perfect example to demonstrate why this can be useful. Before the upgrade, there were no locked objects. You might have some user’s documents, which is obviously fine and you shouldn’t touch them normally, unless you have some external reasons:

[dmadmin@cs-0 ~]$ repo=REPO1
[dmadmin@cs-0 ~]$
[dmadmin@cs-0 ~]$ iapi ${repo} -U${USER} -Pxxx << EOF
> ?,c,select r_object_id, object_name, r_object_type, r_creation_date, r_modify_date, r_lock_owner, r_lock_machine, r_lock_date from dm_sysobject where r_lock_owner!=' ';
> EOF


        EMC Documentum iapi - Interactive API interface
        (c) Copyright EMC Corp., 1992 - 2015
        All rights reserved.
        Client Library Release 7.2.0150.0154


Connecting to Server using docbase REPO1
[DM_SESSION_I_SESSION_START]info:  "Session 010f1234809825ae started for user dmadmin."


Connected to Documentum Server running Release 7.2.0160.0297  Linux64.Oracle
Session id is s0
API> r_object_id       object_name     r_object_type   r_creation_date     r_modify_date       r_lock_owner       r_lock_machine       r_lock_date
----------------  --------------  --------------  ------------------  ------------------  -----------------  -------------------  -----------------
(0 rows affected)

API> Bye
[dmadmin@cs-0 ~]$

Then after the upgrade, there were one locked item:

[dmadmin@cs-0 ~]$ iapi ${repo} -U${USER} -Pxxx << EOF
> ?,c,select r_object_id, object_name, r_object_type, r_creation_date, r_modify_date, r_lock_owner, r_lock_machine, r_lock_date from dm_sysobject where r_lock_owner!=' ';
> EOF


        OpenText Documentum iapi - Interactive API interface
        Copyright (c) 2018. OpenText Corporation
        All rights reserved.
        Client Library Release 16.4.0200.0080


Connecting to Server using docbase REPO1
[DM_SESSION_I_SESSION_START]info:  "Session 010f12348099e600 started for user dmadmin."


Connected to OpenText Documentum Server running Release 16.4.0200.0256  Linux64.Oracle
Session id is s0
API> r_object_id       object_name     r_object_type   r_creation_date     r_modify_date       r_lock_owner       r_lock_machine       r_lock_date
----------------  --------------  --------------  ------------------  ------------------  -----------------  -------------------  -----------------
090f123480000344  Castor          dmc_jar         12/1/2018 08:56:05  12/1/2018 08:56:05  dmadmin            cs-0                 5/7/2020 11:12:12
(1 rows affected)

[dmadmin@cs-0 ~]$

As you can see above, it was an upgrade from 7.2 (the source version doesn’t matter for this issue) to 16.4 P20. The ‘Castor’ object has been locked during the upgrade but it has apparently not been unlocked and it hasn’t been updated either. Therefore, that’s clearly two indicators that something went wrong. Castor is a third party software included by OpenText to provide BPM runtime BOF aspects and TBOs. It is configured as part of the dm_bpmmodules_install EBS script. So, looking at the log file of the EBS script generated during the upgrade showed the following:

[dmadmin@cs-0 ~]$ cat $DOCUMENTUM/dba/config/${repo}/dm_bpmmodules_install.out
Error checking out of object 090f123480000344: [DM_API_E_NO_MATCH]error:  "There was no match in the docbase for the qualification: dmc_jar where object_name = 'BPM XML Schema'"


Failed to create dmc_jar object (Castor)
[dmadmin@cs-0 ~]$

Based on the generated log file, it is clear that something went wrong there… Looking into the repository object, the ‘BPM XML Schema‘ object has been created properly but somehow the error shows that it cannot find it?

[dmadmin@cs-0 ~]$ iapi ${repo} -U${USER} -Pxxx << EOF
> ?,c,select r_object_id, object_name, r_object_type, r_creation_date, r_modify_date, r_lock_owner, r_lock_machine, r_lock_date from dm_sysobject where object_name='BPM XML Schema' OR object_name='Castor';
> EOF


        OpenText Documentum iapi - Interactive API interface
        Copyright (c) 2018. OpenText Corporation
        All rights reserved.
        Client Library Release 16.4.0200.0080


Connecting to Server using docbase REPO1
[DM_SESSION_I_SESSION_START]info:  "Session 010f12348099e62e started for user dmadmin."


Connected to OpenText Documentum Server running Release 16.4.0200.0256  Linux64.Oracle
Session id is s0
API> r_object_id       object_name     r_object_type   r_creation_date     r_modify_date       r_lock_owner       r_lock_machine       r_lock_date
----------------  --------------  --------------  ------------------  ------------------  -----------------  -------------------  -----------------
090f1234809915ae  BPM XML Schema  dmc_jar         5/7/2020 11:12:12   5/7/2020 11:12:12                                           nulldate
090f123480000344  Castor          dmc_jar         12/1/2018 08:56:05  12/1/2018 08:56:05  dmadmin            cs-0                 5/7/2020 11:12:12
(2 rows affected)

API> Bye
[dmadmin@cs-0 ~]$

Since this seemed strange, I opened the OpenText SR#4507002 for them to look into it because the ‘BPM XML Schema‘ object was created but somehow it isn’t found right after while updating the ‘Castor‘ one… If you look at the dates, it clearly shows that there is something fishy here ;). According to OpenText, this is because the message put on the log is actually not the correct error message but a previous message from the execution of the EBS script, so it hides the real issue. The dmbasic code is using an message queue for the errors and as part of the CS 16.4 P10, OpenText updated this EBS script to add an additional jar file apparently. As part of this, the initial message regarding the ‘DM_API_E_NO_MATCH‘ (which seems to be expected) is never flushed and therefore when there is a subsequent error related to the checkout, it is the first error that is displayed in the logs, which isn’t correct since it shows the no match on ‘BPM XML Schema‘ while actually trying to create the ‘Castor‘ object.

They are still working on a fix for this issue, which will probably be integrated into a next patch (Update: I got the feedback that it will be integrated in the CS 16.4 P29, planned for release at the end of September). Until then, you can fix the issue by simply executing the EBS script manually, just don’t forget to unlock the ‘Castor‘ object before executing the EBS script with something like “unlock,c,<r_object_id>” (use the r_object_id of the ‘Castor‘ object obviously). The execution of the EBS script is pretty straightforward:

[dmadmin@cs-0 ~]$ cd $DM_HOME/install/admin
[dmadmin@cs-0 admin]$
[dmadmin@cs-0 admin]$ dmbasic -f dm_bpmmodules_install.ebs -e Install -- ${repo} dmadmin xxx $DM_HOME/lib
[dmadmin@cs-0 admin]$
[dmadmin@cs-0 admin]$ iapi ${repo} -U${USER} -Pxxx << EOF
> ?,c,select r_object_id, object_name, r_object_type, r_creation_date, r_modify_date, r_lock_owner, r_lock_machine, r_lock_date from dm_sysobject where object_name='BPM XML Schema' OR object_name='Castor';
> EOF


        OpenText Documentum iapi - Interactive API interface
        Copyright (c) 2018. OpenText Corporation
        All rights reserved.
        Client Library Release 16.4.0200.0080


Connecting to Server using docbase REPO1
[DM_SESSION_I_SESSION_START]info:  "Session 010f1234809ec2d5 started for user dmadmin."


Connected to OpenText Documentum Server running Release 16.4.0200.0256  Linux64.Oracle
Session id is s0
API> r_object_id       object_name     r_object_type   r_creation_date     r_modify_date       r_lock_owner       r_lock_machine       r_lock_date
----------------  --------------  --------------  ------------------  ------------------  -----------------  -------------------  -----------------
090f1234809ea485  BPM XML Schema  dmc_jar         5/12/2020 20:27:56  5/12/2020 20:27:56                                          nulldate
090f1234809ea48d  Castor          dmc_jar         5/12/2020 20:27:56  5/12/2020 20:27:56                                          nulldate
(2 rows affected)

API> Bye
[dmadmin@cs-0 admin]$

This time, the ‘Castor‘ object has been recreated properly with a new ID, at the exact same time as the ‘BPM XML Schema‘ one and it is not locked anymore. This looks much better, isn’t it?

Cet article Documentum Upgrade – Castor is locked! est apparu en premier sur Blog dbi services.

By Franck Pachot

.
I’ll reference Alex DeBrie article “SQL, NoSQL, and Scale: How DynamoDB scales where relational databases don’t“, especially the paragraph about “Why relational databases don’t scale”. But I want to make clear that my post here is not against this article, but against a very common myth that even precedes NoSQL databases. Actually, I’m taking this article as reference because the author, in his website and book, has really good points about data modeling in NoSQL. And because AWS DynamoDB is probably the strongest NoSQL database today. I’m challenging some widespread assertions and better do it based on good quality content and product.

There are many use cases where NoSQL is a correct alternative, but moving from a relational database system to a key-value store because you heard that “joins don’t scale” is probably not a good reason. You should choose a solution for the features it offers (the problem it solves), and not because you ignore what you current platform is capable of.

time complexity of joins

The idea in this article, taken from the popular Rick Houlihan talk, is that, by joining tables, you read more data. And that it is a CPU intensive operation. And the time complexity of joins is “( O (M + N) ) or worse” according to Alex DeBrie article or “O(log(N))+Nlog(M)” according to Rick Houlihan slide. This makes reference to “time complexity” and “Big O” notation. You can read about it. But this supposes that the cost of a join depends on the size of the tables involved (represented by N and M). That would be right with non-partitioned table full scan. But all relational databases come with B*Tree indexes. And when we compare to a key-value store we are obviously retrieving few rows and the join method will be a Nested Loop with Index Range Scan. This access method is actually not dependent at all on the size of the tables. That’s why relational database are the king of OTLP applications.

Let’s test it

The article claims that “there’s one big problem with relational databases: performance is like a black box. There are a ton of factors that impact how quickly your queries will return.” with an example on a query like: “SELECT * FROM orders JOIN users ON … WHERE user.id = … GROUP BY … LIMIT 20”. It says that “As the size of your tables grow, these operations will get slower and slower.”

I will build those tables, in PostgreSQL here, because that’s my preferred Open Source RDBMS, and show that:

• Performance is not a black box: all RDBMS have an EXPLAIN command that display exactly the algorithm used (even CPU and memory access) and you can estimate the cost easily from it.
• Join and Group By here do not depend on the size of the table at all but only the rows selected. You will multiply your tables by several orders of magnitude before the number of rows impact the response time by a 1/10s of millisecond.

Create the tables

I will create small tables here. Because when reading the execution plan, I don’t need large tables to estimate the cost and the response-time scalability. You can run the same with larger tables if you want to see how it scales. And then maybe investigate further the features for big tables (partitioning, parallel query,…). But let’s start with very simple tables without specific optimization.

\timing
create table USERS ( USER_ID bigserial primary key, FIRST_NAME text, LAST_NAME text)
;
CREATE TABLE
create table ORDERS ( ORDER_ID bigserial primary key, ORDER_DATE timestamp, AMOUNT numeric(10,2), USER_ID bigint, DESCRIPTION text)
;

I have created the two tables that I’ll join. Both with an auto-generated primary key for simplicity.

Insert test data

It is important to build the table as they would be in real life. USERS probably come without specific order. ORDERS come by date. This means that ORDERS from one USER are scattered throughout the table. The query would be much faster with clustered data, and each RDBMS has some ways to achieve this, but I want to show the cost of joining two tables here without specific optimisation.

insert into  USERS (FIRST_NAME, LAST_NAME)
 with
  random_words as (

  select generate_series id,
   translate(md5(random()::text),'-0123456789','aeioughij') as word

  from generate_series(1,100)

  )
 select
  words1.word ,words2.word

  from
   random_words words1
  cross join
   random_words words2
  order by words1.id+words2.id

;
INSERT 0 10000
Time: 28.641 ms

select * from USERS order by user_id fetch first 10 rows only;
 user_id |           first_name           |           last_name
---------+--------------------------------+--------------------------------
       1 | iooifgiicuiejiaeduciuccuiogib  | iooifgiicuiejiaeduciuccuiogib
       2 | iooifgiicuiejiaeduciuccuiogib  | dgdfeeiejcohfhjgcoigiedeaubjbg
       3 | dgdfeeiejcohfhjgcoigiedeaubjbg | iooifgiicuiejiaeduciuccuiogib
       4 | ueuedijchudifefoedbuojuoaudec  | iooifgiicuiejiaeduciuccuiogib
       5 | iooifgiicuiejiaeduciuccuiogib  | ueuedijchudifefoedbuojuoaudec
       6 | dgdfeeiejcohfhjgcoigiedeaubjbg | dgdfeeiejcohfhjgcoigiedeaubjbg
       7 | iooifgiicuiejiaeduciuccuiogib  | jbjubjcidcgugubecfeejidhoigdob
       8 | jbjubjcidcgugubecfeejidhoigdob | iooifgiicuiejiaeduciuccuiogib
       9 | ueuedijchudifefoedbuojuoaudec  | dgdfeeiejcohfhjgcoigiedeaubjbg
      10 | dgdfeeiejcohfhjgcoigiedeaubjbg | ueuedijchudifefoedbuojuoaudec
(10 rows)

Time: 0.384 ms

This generated 10000 users in the USERS table with random names.

insert into ORDERS ( ORDER_DATE, AMOUNT, USER_ID, DESCRIPTION)
 with
  random_amounts as (
      ------------> this generates 10 random order amounts
  select
   1e6*random() as AMOUNT
  from generate_series(1,10)
 )
 ,random_dates as (
      ------------> this generates 10 random order dates
  select
   now() - random() * interval '1 year' as ORDER_DATE
  from generate_series(1,10)
 )
select ORDER_DATE, AMOUNT, USER_ID, md5(random()::text) DESCRIPTION from
  random_dates
 cross join
  random_amounts
 cross join
  users
 order by ORDER_DATE
      ------------> I sort this by date because that's what happens in real life. Clustering by users would not be a fair test.
;
INSERT 0 1000000
Time: 4585.767 ms (00:04.586)

I have now one million orders generated as 100 orders for each users in the last year. You can play with the numbers to generate more and see how it scales. This is fast: 5 seconds to generate 1 million orders here, and there are many way to load faster if you feel the need to test on very large data sets. But the point is not there.

create index ORDERS_BY_USER on ORDERS(USER_ID);
CREATE INDEX
Time: 316.322 ms
alter table ORDERS add constraint ORDERS_BY_USER foreign key (USER_ID) references USERS;
ALTER TABLE
Time: 194.505 ms

As, in my data model, I want to navigate from USERS to ORDERS I add an index for it. And I declare the referential integrity to avoid logical corruptions in case there is a bug in my application, or a human mistake during some ad-hoc fixes. As soon as the constraint is declared, I have no need to check this assertion in my code anymore. The constraint also informs the query planner know about this one-to-many relationship as it may open some optimizations. That’s the relational database beauty: we declare those things rather than having to code their implementation.

vacuum analyze;
VACUUM
Time: 429.165 ms

select version();
                                                 version
---------------------------------------------------------------------------------------------------------
 PostgreSQL 12.3 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit
(1 row)

I’m in PostgreSQL, version 12, on a Linux box with 2 CPUs only. I’ve run a manual VACUUM to get a reproducible testcase rather than relying on autovacuum kicking-in after those table loading.

select relkind,relname,reltuples,relpages,lpad(pg_size_pretty(relpages::bigint*8*1024),20) "relpages * 8k" from pg_class natural join (select oid relnamespace,nspname from pg_namespace) nsp where nspname='public' order by relpages;

 relkind |       relname       | reltuples | relpages |    relpages * 8k
---------+---------------------+-----------+----------+----------------------
 S       | orders_order_id_seq |         1 |        1 |           8192 bytes
 S       | users_user_id_seq   |         1 |        1 |           8192 bytes
 i       | users_pkey          |     10000 |       30 |               240 kB
 r       | users               |     10000 |      122 |               976 kB
 i       | orders_pkey         |     1e+06 |     2745 |                21 MB
 i       | orders_by_user      |     1e+06 |     2749 |                21 MB
 r       | orders              |     1e+06 |    13334 |               104 MB

Here are the sizes of my tables: The 1 million orders take 104MB and the 10 thousand users is 1MB. I’ll increase it later, but I don’t need this to understand the performance predictability.

When understanding the size, remember that the size of the table is only the size of data. Metadata (like column names) are not repeated for each row. They are stored once in the RDBMS catalog describing the table. As PostgreSQL has a native JSON datatype you can also test with a non-relational model here.

Execute the query

select order_month,sum(amount),count(*)
from
  (
  select date_trunc('month',ORDER_DATE) order_month, USER_ID, AMOUNT
  from ORDERS join USERS using(USER_ID)
  ) user_orders
where USER_ID=42
group by order_month
;

     order_month     |     sum     | count
---------------------+-------------+-------
 2019-11-01 00:00:00 |  5013943.57 |    10
 2019-09-01 00:00:00 |  5013943.57 |    10
 2020-04-01 00:00:00 |  5013943.57 |    10
 2019-08-01 00:00:00 | 15041830.71 |    30
 2020-02-01 00:00:00 | 10027887.14 |    20
 2020-06-01 00:00:00 |  5013943.57 |    10
 2019-07-01 00:00:00 |  5013943.57 |    10
(7 rows)

Time: 2.863 ms

Here is the query mentioned in the article: get all orders for one user, and do some aggregation on them. Looking at the time is not really interesting as it depends on the RAM to cache the buffers at database or filesystem level, and disk latency. But we are developers and, by looking at the operations and loops that were executed, we can understand how it scales and where we are in the “time complexity” and “Big O” order of magnitude.

Explain the execution

This is as easy as running the query with EXPLAIN:

explain (analyze,verbose,costs,buffers)
select order_month,sum(amount)
from
  (
  select date_trunc('month',ORDER_DATE) order_month, USER_ID, AMOUNT
  from ORDERS join USERS using(USER_ID)
  ) user_orders
where USER_ID=42
group by order_month
;
                                                                   QUERY PLAN

------------------------------------------------------------------------------------------------------------------------------------------------
 GroupAggregate  (cost=389.34..390.24 rows=10 width=40) (actual time=0.112..0.136 rows=7 loops=1)
   Output: (date_trunc('month'::text, orders.order_date)), sum(orders.amount)
   Group Key: (date_trunc('month'::text, orders.order_date))
   Buffers: shared hit=19
   ->  Sort  (cost=389.34..389.59 rows=100 width=17) (actual time=0.104..0.110 rows=100 loops=1)
         Output: (date_trunc('month'::text, orders.order_date)), orders.amount
         Sort Key: (date_trunc('month'::text, orders.order_date))
         Sort Method: quicksort  Memory: 32kB
         Buffers: shared hit=19
         ->  Nested Loop  (cost=5.49..386.02 rows=100 width=17) (actual time=0.022..0.086 rows=100 loops=1)
               Output: date_trunc('month'::text, orders.order_date), orders.amount
               Buffers: shared hit=19
               ->  Index Only Scan using users_pkey on public.users  (cost=0.29..4.30 rows=1 width=8) (actual time=0.006..0.006 rows=1 loops=1)
                     Output: users.user_id
                     Index Cond: (users.user_id = 42)
                     Heap Fetches: 0
                     Buffers: shared hit=3
               ->  Bitmap Heap Scan on public.orders  (cost=5.20..380.47 rows=100 width=25) (actual time=0.012..0.031 rows=100 loops=1)
                     Output: orders.order_id, orders.order_date, orders.amount, orders.user_id, orders.description
                     Recheck Cond: (orders.user_id = 42)
                     Heap Blocks: exact=13
                     Buffers: shared hit=16
                     ->  Bitmap Index Scan on orders_by_user  (cost=0.00..5.17 rows=100 width=0) (actual time=0.008..0.008 rows=100 loops=1)
                           Index Cond: (orders.user_id = 42)
                           Buffers: shared hit=3
 Planning Time: 0.082 ms
 Execution Time: 0.161 ms

Here is the execution plan with the execution statistics. We have read 3 pages from USERS to get our USER_ID (Index Only Scan) and navigated, with Nested Loop, to ORDERS and get the 100 orders for this user. This has read 3 pages from the index (Bitmap Index Scan) and 13 pages from the table. That’s a total of 19 pages. Those pages are 8k blocks.

4x initial size scales with same performance: 19 page reads

Let’s increase the size of the tables by a factor 4. I change the “generate_series(1,100)” to “generate_series(1,200)” in the USERS generations and run the same. That generates 40000 users and 4 million orders.

select relkind,relname,reltuples,relpages,lpad(pg_size_pretty(relpages::bigint*8*1024),20) "relpages * 8k" from pg_class natural join (select
oid relnamespace,nspname from pg_namespace) nsp where nspname='public' order by relpages;

 relkind |       relname       |  reltuples   | relpages |    relpages * 8k
---------+---------------------+--------------+----------+----------------------
 S       | orders_order_id_seq |            1 |        1 |           8192 bytes
 S       | users_user_id_seq   |            1 |        1 |           8192 bytes
 i       | users_pkey          |        40000 |      112 |               896 kB
 r       | users               |        40000 |      485 |              3880 kB
 i       | orders_pkey         |        4e+06 |    10969 |                86 MB
 i       | orders_by_user      |        4e+06 |    10985 |                86 MB
 r       | orders              | 3.999995e+06 |    52617 |               411 MB

explain (analyze,verbose,costs,buffers)
select order_month,sum(amount)
from
  (
  select date_trunc('month',ORDER_DATE) order_month, USER_ID, AMOUNT
  from ORDERS join USERS using(USER_ID)
  ) user_orders
where USER_ID=42
group by order_month
;
explain (analyze,verbose,costs,buffers)
select order_month,sum(amount)
from
  (
  select date_trunc('month',ORDER_DATE) order_month, USER_ID, AMOUNT
  from ORDERS join USERS using(USER_ID)
  ) user_orders
where USER_ID=42
group by order_month
;
                                                                   QUERY PLAN                                                                 
------------------------------------------------------------------------------------------------------------------------------------------------
 GroupAggregate  (cost=417.76..418.69 rows=10 width=40) (actual time=0.116..0.143 rows=9 loops=1)
   Output: (date_trunc('month'::text, orders.order_date)), sum(orders.amount)
   Group Key: (date_trunc('month'::text, orders.order_date))
   Buffers: shared hit=19
   ->  Sort  (cost=417.76..418.02 rows=104 width=16) (actual time=0.108..0.115 rows=100 loops=1)
         Output: (date_trunc('month'::text, orders.order_date)), orders.amount
         Sort Key: (date_trunc('month'::text, orders.order_date))
         Sort Method: quicksort  Memory: 32kB
         Buffers: shared hit=19
         ->  Nested Loop  (cost=5.53..414.27 rows=104 width=16) (actual time=0.044..0.091 rows=100 loops=1)
               Output: date_trunc('month'::text, orders.order_date), orders.amount
               Buffers: shared hit=19
               ->  Index Only Scan using users_pkey on public.users  (cost=0.29..4.31 rows=1 width=8) (actual time=0.006..0.007 rows=1 loops=1)
                     Output: users.user_id
                     Index Cond: (users.user_id = 42)
                     Heap Fetches: 0
                     Buffers: shared hit=3
               ->  Bitmap Heap Scan on public.orders  (cost=5.24..408.66 rows=104 width=24) (actual time=0.033..0.056 rows=100 loops=1)
                     Output: orders.order_id, orders.order_date, orders.amount, orders.user_id, orders.description
                     Recheck Cond: (orders.user_id = 42)
                     Heap Blocks: exact=13
                     Buffers: shared hit=16
                     ->  Bitmap Index Scan on orders_by_user  (cost=0.00..5.21 rows=104 width=0) (actual time=0.029..0.029 rows=100 loops=1)
                           Index Cond: (orders.user_id = 42)
                           Buffers: shared hit=3
 Planning Time: 0.084 ms
 Execution Time: 0.168 ms
(27 rows)

Time: 0.532 ms

Look how we scaled here: I multiplied the size of the tables by 4x and I have exactly the same cost: 3 pages from each index and 13 from the table. This is the beauty of B*Tree: the cost depends only on the height of the tree and not the size of the table. And you can increase the table exponentially before the height of the index increases.

16x initial size scales with 21/19=1.1 cost factor

Let’s go further and x4 the size of the tables again. I run with “generate_series(1,400)” in the USERS generations and run the same. That generates 160 thousand users and 16 million orders.

select relkind,relname,reltuples,relpages,lpad(pg_size_pretty(relpages::bigint*8*1024),20) "relpages * 8k" from pg_class natural join (select
oid relnamespace,nspname from pg_namespace) nsp where nspname='public' order by relpages;
 relkind |       relname       |  reltuples   | relpages |    relpages * 8k
---------+---------------------+--------------+----------+----------------------
 S       | orders_order_id_seq |            1 |        1 |           8192 bytes
 S       | users_user_id_seq   |            1 |        1 |           8192 bytes
 i       | users_pkey          |       160000 |      442 |              3536 kB
 r       | users               |       160000 |     1925 |                15 MB
 i       | orders_pkey         |      1.6e+07 |    43871 |               343 MB
 i       | orders_by_user      |      1.6e+07 |    43935 |               343 MB
 r       | orders              | 1.600005e+07 |   213334 |              1667 MB

explain (analyze,verbose,costs,buffers)
select order_month,sum(amount)
from
  (
  select date_trunc('month',ORDER_DATE) order_month, USER_ID, AMOUNT
  from ORDERS join USERS using(USER_ID)
  ) user_orders
where USER_ID=42
group by order_month
;
                                                                   QUERY PLAN                                                                 
------------------------------------------------------------------------------------------------------------------------------------------------
 GroupAggregate  (cost=567.81..569.01 rows=10 width=40) (actual time=0.095..0.120 rows=8 loops=1)
   Output: (date_trunc('month'::text, orders.order_date)), sum(orders.amount)
   Group Key: (date_trunc('month'::text, orders.order_date))
   Buffers: shared hit=21
   ->  Sort  (cost=567.81..568.16 rows=140 width=17) (actual time=0.087..0.093 rows=100 loops=1)
         Output: (date_trunc('month'::text, orders.order_date)), orders.amount
         Sort Key: (date_trunc('month'::text, orders.order_date))
         Sort Method: quicksort  Memory: 32kB
         Buffers: shared hit=21
         ->  Nested Loop  (cost=6.06..562.82 rows=140 width=17) (actual time=0.026..0.070 rows=100 loops=1)
               Output: date_trunc('month'::text, orders.order_date), orders.amount
               Buffers: shared hit=21
               ->  Index Only Scan using users_pkey on public.users  (cost=0.42..4.44 rows=1 width=8) (actual time=0.007..0.007 rows=1 loops=1)
                     Output: users.user_id
                     Index Cond: (users.user_id = 42)
                     Heap Fetches: 0
                     Buffers: shared hit=4
               ->  Bitmap Heap Scan on public.orders  (cost=5.64..556.64 rows=140 width=25) (actual time=0.014..0.035 rows=100 loops=1)
                     Output: orders.order_id, orders.order_date, orders.amount, orders.user_id, orders.description
                     Recheck Cond: (orders.user_id = 42)
                     Heap Blocks: exact=13
                     Buffers: shared hit=17
                     ->  Bitmap Index Scan on orders_by_user  (cost=0.00..5.61 rows=140 width=0) (actual time=0.010..0.010 rows=100 loops=1)
                           Index Cond: (orders.user_id = 42)
                           Buffers: shared hit=4
 Planning Time: 0.082 ms
 Execution Time: 0.159 ms

Yes, by increasing the table size a lot the index may have to split the root block to add a new branch level. The consequence is minimal: two additional pages to read here. The additional execution time is in tens of microseconds when cached in RAM, up to milliseconds if from mechanical disk. With 10x or 100x larger tables, you will do some physical I/O and only the top index branches will be in memory. You can expect about about 20 I/O calls then. With SSD on Fiber Channel (like with AWS RDS PostgreSQL for example), this will still be in single-digit millisecond. The cheapest AWS EBS Provisioned IOPS for RDS is 1000 IOPS then you can estimate the number of queries per second you can run. The number of pages here (“Buffers”) is the right metric to estimate the cost of the query. To be compared with DynamoDB RCU.

64x initial size scales with 23/19=1.2 cost factor

Last test for me, but you can go further, I change to “generate_series(1,800)” in the USERS generations and run the same. That generates 640 thousand users and 64 million orders.

select relkind,relname,reltuples,relpages,lpad(pg_size_pretty(relpages::bigint*8*1024),20) "relpages * 8k" from pg_class natural join (select
oid relnamespace,nspname from pg_namespace) nsp where nspname='public' order by relpages;

 relkind |       relname       |   reltuples   | relpages |    relpages * 8k
---------+---------------------+---------------+----------+----------------------
 S       | orders_order_id_seq |             1 |        1 |           8192 bytes
 S       | users_user_id_seq   |             1 |        1 |           8192 bytes
 i       | users_pkey          |        640000 |     1757 |                14 MB
 r       | users               |        640000 |     7739 |                60 MB
 i       | orders_pkey         |       6.4e+07 |   175482 |              1371 MB
 i       | orders_by_user      |       6.4e+07 |   175728 |              1373 MB
 r       | orders              | 6.4000048e+07 |   853334 |              6667 MB


explain (analyze,verbose,costs,buffers)
select order_month,sum(amount)
from
  (
  select date_trunc('month',ORDER_DATE) order_month, USER_ID, AMOUNT
  from ORDERS join USERS using(USER_ID)
  ) user_orders
where USER_ID=42
group by order_month
;
                                                                QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------------
 HashAggregate  (cost=1227.18..1227.33 rows=10 width=40) (actual time=0.102..0.105 rows=7 loops=1)
   Output: (date_trunc('month'::text, orders.order_date)), sum(orders.amount)
   Group Key: date_trunc('month'::text, orders.order_date)
   Buffers: shared hit=23
   ->  Nested Loop  (cost=7.36..1225.65 rows=306 width=17) (actual time=0.027..0.072 rows=100 loops=1)
         Output: date_trunc('month'::text, orders.order_date), orders.amount
         Buffers: shared hit=23
         ->  Index Only Scan using users_pkey on public.users  (cost=0.42..4.44 rows=1 width=8) (actual time=0.007..0.008 rows=1 loops=1)
               Output: users.user_id
               Index Cond: (users.user_id = 42)
               Heap Fetches: 0
               Buffers: shared hit=4
         ->  Bitmap Heap Scan on public.orders  (cost=6.94..1217.38 rows=306 width=25) (actual time=0.015..0.037 rows=100 loops=1)
               Output: orders.order_id, orders.order_date, orders.amount, orders.user_id, orders.description
               Recheck Cond: (orders.user_id = 42)
               Heap Blocks: exact=15
               Buffers: shared hit=19
               ->  Bitmap Index Scan on orders_by_user  (cost=0.00..6.86 rows=306 width=0) (actual time=0.011..0.011 rows=100 loops=1)
                     Index Cond: (orders.user_id = 42)
                     Buffers: shared hit=4
 Planning Time: 0.086 ms
 Execution Time: 0.134 ms
(22 rows)

Time: 0.521 ms

You see how the cost increases slowly, with two additional pages to read here.

Please, test with more rows. When looking at the time (less than 1 millisecond), keep in mind that it is CPU time here as all pages are in memory cache. On purpose, because the article mentions CPU and RAM (“joins require a lot of CPU and memory”). Anyway, 20 disk reads will still be within the millisecond on modern storage.

Time complexity of B*Tree is actually very light

Let’s get back to the “Big O” notation. We are definitely not “O (M + N)”. This would have been without any index, where all pages from all tables would have been full scanned. Any database maintains hashed or sorted structures to improve high selectivity queries. This has nothing to do with SQL vs. NoSQL or with RDBMS vs. Hierarchichal DB. In DynamoDB this structure on primary key is HASH partitioning (and additional sorting). In RDBMS the most common structure is a sorted index (with the possibility of additional partitioning, zone maps, clustering,…). We are not in “O(log(N))+Nlog(M)” but more like “O(log(N))+log(M)” because the size of the driving table (N) has nothing to do on the inner loop cost. The first filtering, the one with “O(log(N))”, has filtered out those N rows. Using “N” and ignoring the outer selectivity is a mistake. Anyway, this O(log) for B*Tree is really scalable as we have seen because the base of this log() function is really small (thanks to large branch blocks – 8KB).

Anyway, the point is not there. As you have seen, the cost of Nested Loop is in the blocks that are fetched from the inner loop, and this depends on the selectivity and the clustering factor (the table physical order correlation with the index order), and some prefetching techniques. This O(log) for going through the index is often insignificant on Range Scans.

40 years of RDBMS optimizations

If you have a database size that is several order of magnitude from those million rows, and where this millisecond latency is a problem, the major RDBMS offer many features and structures to go further in performance and predictability of response time. As we have seen, the cost of this query is not about Index, Nested Loop or Group By. It is about the scattered items: ingested by date but queried by user.

Through its 40 years of optimizing OLTP applications, the Oracle Database have a lot of features, with their popularity depending on the IT trends. From the first versions, in the 80’s, because the hierarchical databases were still in people’s mind, and the fear of “joins are expensive” was already there, Oracle has implemented a structure to store the tables together, pre-joined. This is called CLUSTER. It was, from the beginning, indexed with a sorted structure (INDEX CLUSTER) or a hashed structure (HASH CLUSTER). Parallel Query was quickly implemented to scale-up and, with Parallel Server now known as RAC, to scale-out. Partitioning was introduced to scale further, again with sorted (PARTITION by RANGE) or hashed (PARTITION BY HASH) segments. This can scale further the index access (LOCAL INDEX with partition pruning). And it also scales joins (PARTITION-WISE JOIN) to reduce CPU and RAM to join large datasets. When more agility was needed, B*Tree sorted structures were the winner and Index Organized Tables were introduced to cluster data (to avoid the most expensive operation as we have seen in the examples above). But Heap Tables and B*Tree are still the winners given their agility and because the Join operations were rarely a bottleneck. Currently, partitioning has improved (even scaling horizontally beyond the clusters with sharding), as well as data clustering (Attribute Clustering, Zone Maps and Storage Index). And there’s always the possibility for Index Only access, just by adding more columns to the index, removing the major cost of table access. And materialized views can also act as pre-built join index and will also reduce the CPU and RAM required for GROUP BY aggregation.

I listed a lot of Oracle features, but Microsoft SQL Server has also many similar features. Clustered tables, covering indexes, Indexed Views, and of course partitioning. Open source databases are evolving a lot. PostgreSQL has partitioning, parallel query, clustering,.. Still Open Source, you can web-scale it to a distributed database with YugabyteDB. MySQL is evolving a lot recently. I’ll not list all databases and all features. You can port the testcase to other databases easily.

Oh, and by the way, if you want to test it on Oracle Database you will quickly realize that the query from the article may not even do any Join operation. Because when you query with the USER_ID you probably don’t need to get back to the USERS table. And thanks to the declared foreign key, the optimizer knows that the join is not necessary: https://dbfiddle.uk/?rdbms=oracle_18&fiddle=a5afeba2fdb27dec7533545ab0a6eb0e.

NoSQL databases are good for many use-cases. But remember that it is a key-value optimized data store. When you start to split a document into multiple entities with their own keys, remember that relational databases were invented for that. I blogged about another myth recently: The myth of NoSQL (vs. RDBMS) agility: adding attributes. All feedback welcome, here or on Twitter:

A new blog post on another myth in NoSQL vs. RDBMS:
“joins dont scale”https://t.co/u4aBE4HXb7

— Franck Pachot (@FranckPachot) July 5, 2020

Cet article The myth of NoSQL (vs. RDBMS) “joins dont scale” est apparu en premier sur Blog dbi services.

My Background

Since I started at dbi services sa, I was working and preparing for SUSE Linux Enterprise 15 certification. I had worked with other Linux distributions like CentOS, Ubuntu and Debian. With my basic Linux knowledge I was able to administrate Apache and nginx with virtual hosts, SSL Encryption with Let’s Encrypt, installing and configuring MySQL Database, opening/closing ports for services with firewall-cmd, network configuration and other basic requirements for Linux Administrating. Before I startet working at dbi services sa, my goal was to get the Red Hat Certified System Administrator (RHCSA^®) certification. With every certification you are filling your backpack, so it’s important for your career. Therefore dbi services sa give me a lot of time for preparing for the SUSE 15 certification, which is awesome!

Why SUSE? And not RHCSA?

Maybe you will ask me why I’m doing SUSE 15 certification instead of RHCSA. The answer is simple: In our company we have few employees which have the RHSCA already. The company needs also employees which has the SUSE 15 certification. The difference between this two certification are also, SUSE is asking you just theoretical multiple choice questions, while RHSCA is a practical exam on a Virtual Machine. This is very important point. In my opinion, practical exam is much more important and meaningful. Why? For example in Linux you can set a static IP Address with nmtui, nmcli or over the GUI. So you have the choice, how you want to configure your Network. RHSCA is just looking the results, if you were able to set the IP Address correctly, you get your points. In reality it is the same: Your manager doesn’t matter which command you use, he/she want’s just that the task is done.

Cet article How to prepare for the SLES 15 Admin certification est apparu en premier sur Blog dbi services.

Introduction

Cloud, Cloud, Cloud. Everyone is talking about the Cloud but a lot of people are still in the fog with Cloud technologies. Let’s talk about basic features of the Oracle Cloud, called OCI for Oracle Cloud Infrastructure.

What is really OCI?

OCI is physically a lot of servers in datacenters all around the world. These servers are not very different from the servers you probably have in your own datacenter. Some of these servers are already in use by the customers, and some are immediately available for existing customers or new customers. Most of the customers will not use complete servers but part of them, thanks to the virtualization layer on OCI. A real server can hold several virtual servers, quite a lot actually. Oracle tells us that there is no overprovisionning on OCI: if you create your own server with 2 CPUs and 64GB of RAM, you’re pretty sure that these resources are available for you on the physical server, even if you don’t plan to use them at full throttle. If you need a complete physical server for yourself, it’s also possible, and it’s easy to provision just like a virtual machine.

What do I need to create a server in OCI?

OCI is actually available through a website, the OCI console, but you’ll have to buy Cloud credits to be able to create resources in this Cloud.

Two other options are available:
– ask your Oracle software provider for free trial Cloud credits for testing OCI
– create a free account and use only always-free resources (quite limitating)

When you’re connected to your brand new OCI account onto the console, just create a compute instance. A compute instance is a server for multi-purpose usage. Several options are available at server creation, like the number of CPUs, the amount of RAM, the size of the boot disk, and the OS that will come pre-installed. Provisionning a simple Linux server takes 2 minutes. Deleting a server is also a matter of minutes.

Can I go straight to server creation?

Not really. You cannot simply create a server, because you’ll need to put this server in a compartment, a kind or virtual container for your servers. So first step is to create a compartment. Compartments are fully isolated between them.

Then, you’ll need a private network (called Virtual Cloud Network or VCN) where to put your server. This private network should be created with care because it cannot overlap your on-premise network, especially if you plan to connect them (you surely need to). With network creation, other basic network components need to be also configured.

What are the basic network resources to configure?

First of all, all these resources are virtual resources in OCI. When configuring your network, you’ll also need at least one subnet from your VCN, a firewall (called security list), a router (route table) and a gateway for connecting this server (NAT gateway for outbound internet connexion or internet gateway for both inbound and outbound connexions).

Your OCI network will be linked to your on-premise network with IPSec VPN technology or FastConnect. This last option being a dedicated connexion to your existing infrastructure that does not go through internet.

So before creating your first server, you’ll need to define and configure all these network settings properly.

How to connect to this server?

If you don’t want to configure a VPN or a FastConnect link for now, you can associate your compute instance to an internet gateway to make it available from everywhere. Security is achieved with SSH keys: you provide your public key(s) on the OCI console for this server, and only you will be able to establish a connexion to your server. Later, a VPN or FastConnect configuration will let you reach all your OCI servers as if they were on your network.

What are the other services available?

If you’re thinking about OCI, it’s probably because you do not only need servers: you need Oracle databases. Actually, you don’t have to provision compute instances to install databases on it. You can directly provision databases, for various versions, Standard or Enterprise Edition, with you own license or without any license (the license fee will be billed as if it were an OCI resource – on a monthly basis). For sure, an underlying server will be provisionned, but you don’t have to create it as a separate task. If you need to connect later to this server, it’s possible as if it were a normal compute instance.

A key feature of OCI is what they call autonomous database: it’s a self-managed database that doesn’t give you access to the server or even the SYSDBA role on the database. You control this kind of DB through a dedicated interface (for loading data for example) and let Oracle automatically manage the classic DBA tasks, even those high-level. Autonomous database comes in two flavours: OLTP or Datawarehouse. Embedded autonomous engine will act differently.

Database services also come with automatic backup you can simply configure when creating the database (or after). Just define what kind of backup you need (mainly choose from various retentions and frequencies) and RMAN will automatically take care of your backups. Restore can be done directly through the OCI console.

Other services are also available, like load balancer or MySQL databases. Some services are free, some come at a cost.

How about the storage?

Multiple storage options are available for your servers depending on your needs:
– block storage: this is similar to LUNs on SAN. Choose the size at block storage creation and plug this storage to your server for a dedicated use
– file storage: this is similar to NFS. A shared storage for multiple servers
– object storage: this storage is usefull to make some files available wherever you need, just by sharing a link

Storage on OCI only relies on SSD disks, so expect high performances regarding I/Os.

How much it costs?

That’s the most difficult question, because you’ll have to define your needs, build your infrastructure on paper, then compute the cost with a cost calculator provided by Oracle. There is two billing options available at this moment: prepaid, with Universal Cloud Credits, or pay-as-you-go based on service utilization. The costs may vary depending on multiple parameters. Base budget for an OCI infrastructure starts from 1000$ a month. Don’t expect an OCI infrastructure to be much less expensive than on-premise servers: it’s mainly interesting because you don’t bother with budgeting, buying, deploying, managing servers on your own. And think about how quick you can deploy a new environment, or destroy an old one. It’s another way of spending your IT budget.

The cost calculator is here.

Conclusion

OCI is a mature Cloud, ready for production and with multiple services available and evolving constantly. Test-it to discover how powerfull it is and make sure to understand all the benefits you can get compared to on-premise solutions.

Cet article Oracle Cloud basics for beginners est apparu en premier sur Blog dbi services.

My Background
Since I started at dbi services sa (before 3 Weeks), I was working and preparing for the SUSE Linux Enterprise 15 certification. I had worked with other Linux distributions like CentOS, Ubuntu and Debian on my old employer. With my basic Linux knowledge I was able to administrate Apache and nginx with virtual hosts, SSL Encryption with Let’s Encrypt, installing and configuring MySQL Database, opening/closing ports for services with firewall-cmd, network configuration and other basic requirements for Linux Administrating. Before I started to working at dbi services sa, my goal was to get the Red Hat Certified System Administrator (RHCSA^®), to get be Linux certificated. If you want proove your skills, you need to be get certificated. With every certification you are filling your backpack, so it’s important for your career. Dbi services sa gave me a lot of time to prepare myself to get the SUSE 15 certification, which is awesome!

Why SUSE? And not RHCSA?
Maybe you will ask me why I’m doing SUSE 15 certification instead of RHCSA. The answer is simple: In our company we have few employees which have the RHSCA already. Our company needs also employees which has the SUSE 15 certification. There are also differences between this two certifications: SUSE is asking you just theoretical multiple choice questions, while RHSCA is a practical exam on a Virtual Machine. This is very important point. In my opinion, practical exam is much more important and meaningful. Why? For example in Linux you can set a static IP Address with nmtui, nmcli or over the GUI. So you have the choice, how you want to configure your Network. RHSCA is just looking the results, if you were able to set the IP Address correctly, you get your points. In reality it is the same: Your manager doesn’t matter which command you use, he/she want’s just that the task is done. Therefore why I recommend you to get the RHSCA instead of SUSE, if your employer not needs an SUSE expert.

My experience with SUSE 15 certification
On my first exam I had 64%, second 65% and third 68% scores. Normally with more than 70% correct answer you will pass the exam and get your certification, I did pass the exam with 68% . I have never done an exam front of my Laptop. During the exam you need to share your camera and screen. Before you can start with the exam, you need to show your ID card, the room and under your desk. Your desk need’s to be empty, no gadgets should be there. You know that someone is watching you, but you don’t know who. Maybe you will say that is not important. But you can not feel free and relax during the exam. Chewing gum are also not allowed. As we are humans and not robots, we lose the concentration after ~35-40 Minutes doing the same thing. But if you do something practical, it’s different. You are reading, typing, solving issues. While on theoretical exam you just reading and selecting the correct answer. A glass of Water is not allowed, while Burger and Grill are allowed   Joke, your doing an exam, it’s a normal healthy human understanding. I recommend you minimum 1 liter cold Water. Once you lose your concentration, just drink water and you will be refreshed.

Choose correct time
On the first exams which I answered 64% and 65% correctly, it was 10:00 AM. The third exam I had done at 04:00 PM and answered 68% correctly. I really recommend you to choose the time as well. The Problem doing the exam in the morning are: You are not fit. Your Brain did’t had enough oxygen for doing an exam front of your Laptop. Also don’t do the exam between 12:00 AM and 14:30 PM! After the Lunch (Don’t eat too much) you will be tired   and can’t focus on the questions.

Preparing for the SUSE certification
I had access to SUSE Training Plattform. There were Online Videos for each Objectives to get be introduced to SUSE. If you have never used Linux before, it’s absolutely the correct place to start. But if you before used and administrated Linux systems like me, you already know the basics of the Linux. So you want pass the exam and not lose your valuable time for “boring” Videos. In the SUSE Training Plattform are also questions for each Objectives. This is very helpful for preparing the exam. For my daily work with Linux I learned a lot of tricks watching this Videos, but this doesn’t help you to pass the exam. My Hint: Download the PDF slides and start learning by doing. If you don’t understand something, you can ask search engines and you will get very simple answer. The explanation in Video can sometimes be difficult to understand. Therefore I’m warmly recommend you learning by doing.

Understand the grub and grub2 like a pro
I don’t know why SUSE is strongly focusing on GRUB2, in the reality I never used. But you should know how you can customize the boot menu and adding your own menus. You should know where you can find this configuration files in the theoretical. In Practical you can use ls to list the directory or the find command to find any files and use the man pages how to add custom menus.

Think logical
Most of Linux commands are very simple. Mostly there are no dash in commands. There are some tricky and common questions. For example:
“How is the graphical version of YaST started from the command line? (Select one)”
You have five answers to choice:

• yast
• yast2
• The graphical version of YaST cannot be started from the command line
• YaST2
• yast-gui

As you can see, this a common question. If you run yast and yast2 command on SUSE Server, you will lunch the graphical version. But the correct answer is yast2.

Unit File
You should know what’s happening in the background once you run the “systemctl stop apache2” command. Yes it’s stopping the apache, but it’s calling the Unit File. You should know where the Unit files are located and you can modify them. You should know why there are RequiredBy or WantetBy in Unit Files etc.

File Systems
SUSE is coming out of box with btrfs file system. So it’s clearly that you will be asked about btrfs. Understand correctly about subvolumes and mounting.

My hints to pass the exam:

• Download the PDF and learn it by doing. (Most words which is bold, they will be asked)
• Check the questions on SUSE Training Platform
• Understand everything, if you have questions ask google to understand
• Book the exam in the afternoon
• Don’t spend a lot of time front of your monitor before the exam.
• Before the exam, open your windows and meantime go to walk, or just go outside
• Water: Put cold water on your desk
• Read the questions correctly
• Think logical, if you don’t know the answer, set the flag and just continue to the next question

Conclusion
I hope this Blog will help you little bit to get your certification. Don’t give up and improve your skills by learning by doing.

Cet article How to prepare for the SLES 15 Admin certification. est apparu en premier sur Blog dbi services.

As you probably heard if you weren’t in an underground bunker for the past 2 years, Oracle changed the licensing of the Oracle JDK. If you want to read more about it, there is a good FAQ here. This obviously had some important repercussions everywhere and Documentum wasn’t exempted. I would have a lot to say about the way OpenText tried to adapt since Documentum 16.4 (and kind of failed) but that’s not really the topic of this blog. Because of this change on Oracle side, many applications started to support the OpenJDK and move from Java 8 to Java 11 or above. In this blog, I wanted to talk about the issue that you will face if you ever try to install DARs using Java 11.

The support for Java 11 has been introduced with Documentum 16.4, either Oracle JDK or OpenJDK. However, by default, the CS 16.4 still included an Oracle JDK 1.8u152 ($DOCUMENTUM/java64/JAVA_LINK) and if you were to try to use Java 11 with the CS 16.4, you would face & see some “funny” things. In a previous blog, I showed how it was possible to deploy DARs using a simple script and I have been using this for years without problem or rather that is until the use of Java 11. In this blog, I will use a Documentum 20.2 environment installed and configured to use an external OpenJDK 11.0.7 (not pre-packaged with the binaries).

Running the usual script to install some DARs with Java 11 ends-up with the following:

[dmadmin@cs-0 scripts]$ java -version
openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment 18.9 (build 11.0.7+10)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.7+10, mixed mode)
[dmadmin@cs-0 scripts]$
[dmadmin@cs-0 scripts]$ cat deploy-all.sh
#!/bin/bash
docbases="GR_REPO1"
dar_list="D2-DAR.dar"
username="dmadmin"
dar_location="$DM_HOME/install/DARsInternal"
password="xxx"

old_ifs=${IFS}
for docbase in ${docbases}; do
  IFS=','; for dar in ${dar_list}; do
    dar_name=${dar##*/}

    echo "Deploying ${dar_name} into ${docbase}"
    ts=$(date "+%Y%m%d-%H%M%S")

    $JAVA_HOME/bin/java -Ddar="${dar_location}/${dar}" \
        -Dlogpath="${dar_location}/dar-deploy-${dar_name}-${docbase}-${ts}.log" \
        -Ddocbase=${docbase} -Duser=${username} -Ddomain= -Dpassword="${password}" \
        -cp $DM_HOME/install/composer/ComposerHeadless/startup.jar \
        org.eclipse.core.launcher.Main \
        -data $DM_HOME/install/composer/workspace \
        -application org.eclipse.ant.core.antRunner \
        -buildfile $DM_HOME/install/composer/deploy.xml

    if [[ ${?} != 0 ]]; then
      echo "ERROR - There was an error while installing the DAR '${dar_name}' into '${docbase}'"
      exit 1
    fi
  done
done
IFS=${old_ifs}
[dmadmin@cs-0 scripts]$
[dmadmin@cs-0 scripts]$ . ./deploy-all.sh
Deploying D2-DAR.dar into GR_REPO1
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.eclipse.osgi.internal.baseadaptor.BaseStorage (file:$DM_HOME/install/composer/ComposerHeadless/plugins/org.eclipse.osgi_3.8.1.v20120830-144521.jar) to method java.net.URLClassLoader.addURL(java.net.URL)
WARNING: Please consider reporting this to the maintainers of org.eclipse.osgi.internal.baseadaptor.BaseStorage
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
An error has occurred. See the log file
$DM_HOME/install/composer/ComposerHeadless/configuration/1593386605194.log.
ERROR - There was an error while installing the DAR 'D2-DAR.dar' into 'GR_REPO1'
[dmadmin@cs-0 scripts]$

Ignore the “WARNING” messages above, it is something that was added in Java 9 and if you want to read more about it, you can check this post. As you can see, the script fails and give you back a nice log file with 5 000+ lines full of strange messages and errors like:

!ENTRY org.eclipse.equinox.simpleconfigurator 4 0 2020-06-28 23:23:25.599
!MESSAGE FrameworkEvent ERROR
!STACK 0
org.osgi.framework.BundleException: The bundle "org.eclipse.equinox.simpleconfigurator_1.0.301.v20120828-033635 [1]" could not be resolved. Reason: Missing Constraint: Bundle-RequiredExecutionEnvironment: CDC-1.1/Foundation-1.1,J2SE-1.4
        at org.eclipse.osgi.framework.internal.core.AbstractBundle.getResolverError(AbstractBundle.java:1332)
        at org.eclipse.osgi.framework.internal.core.AbstractBundle.getResolutionFailureException(AbstractBundle.java:1316)
        at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:323)
        at org.eclipse.osgi.framework.internal.core.AbstractBundle.resume(AbstractBundle.java:390)
        at org.eclipse.osgi.framework.internal.core.Framework.resumeBundle(Framework.java:1176)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:559)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:544)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.incFWSL(StartLevelManager.java:457)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:243)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:438)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:1)
        at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
        at org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:340)

!ENTRY org.eclipse.equinox.common 4 0 2020-06-28 23:23:25.602
!MESSAGE FrameworkEvent ERROR
!STACK 0
org.osgi.framework.BundleException: The bundle "org.eclipse.equinox.common_3.6.100.v20120522-1841 [59]" could not be resolved. Reason: Missing Constraint: Bundle-RequiredExecutionEnvironment: CDC-1.1/Foundation-1.1,J2SE-1.4
        at org.eclipse.osgi.framework.internal.core.AbstractBundle.getResolverError(AbstractBundle.java:1332)
        at org.eclipse.osgi.framework.internal.core.AbstractBundle.getResolutionFailureException(AbstractBundle.java:1316)
        at org.eclipse.osgi.framework.internal.core.BundleHost.startWorker(BundleHost.java:323)
        at org.eclipse.osgi.framework.internal.core.AbstractBundle.resume(AbstractBundle.java:390)
        at org.eclipse.osgi.framework.internal.core.Framework.resumeBundle(Framework.java:1176)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:559)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.resumeBundles(StartLevelManager.java:544)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.incFWSL(StartLevelManager.java:457)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.doSetStartLevel(StartLevelManager.java:243)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:438)
        at org.eclipse.osgi.framework.internal.core.StartLevelManager.dispatchEvent(StartLevelManager.java:1)
        at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
        at org.eclipse.osgi.framework.eventmgr.EventManager$EventThread.run(EventManager.java:340)

...

!ENTRY org.eclipse.osgi 4 0 2020-06-28 23:23:25.895
!MESSAGE Application error
!STACK 1
java.lang.IllegalStateException: Unable to acquire application service. Ensure that the org.eclipse.core.runtime bundle is resolved and started (see config.ini).
        at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:74)
        at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
        at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
        at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
        at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
        at org.eclipse.equinox.launcher.Main.main(Main.java:1414)
        at org.eclipse.core.launcher.Main.main(Main.java:34)

What happen is that to deploy DARs, the script is using the Composer Headless. It is a very old software that is present since the creation of the universe (almost) and it doesn’t support Java 11 at all. With Documentum 16.4, since an Oracle JDK 8u152 was shipped with the binaries, it wasn’t an issue to deploy DARs. However, with newer version of the Content Server like 20.2, you can technically install Documentum from scratch using an external Java 11. That being said, since the InstallAnywhere packages (as far as I know) and the Composer Headless do not support Java 11, OpenText included some old JDK 8 here and there to do the needed jobs.

In 20.2 for example, you will find an Oracle JDK 8u202 inside the Composer Headless for DAR installation. Documentum uses this whenever a DAR install is needed: Repository, D2, BPM/xCP, aso… You can find the information about the Oracle JDK 8 in the dardeployer.ini configuration file:

[dmadmin@cs-0 scripts]$ cat $DM_HOME/install/composer/ComposerHeadless/dardeployer.ini
-vm
$DM_HOME/install/composer/ComposerHeadless/java/jdk1.8.0_202_x64/bin
-vm
./java/jdk1.8.0_202_x64/bin
-configuration
darinstallerconfiguration
--launcher.XXMaxPermSize
256m
-vmargs
-Xms40m
-Xmx512m
-XX:MaxPermSize=256m
[dmadmin@cs-0 scripts]$

What does that mean for the script to deploy DARs? Well, what might be the simplest solution to keep backward compatibility with older versions of Documentum as well would be to use the Java shipped in the Composer Headless, if any, and otherwise use the global JDK referenced in the JAVA_HOME environment variable. The problem is that OpenText keeps changing their packaging and it will probably continue to change in the future, so I believe it’s important to stay as agile and generic as possible. It would be possible to fetch the Java path from the dardeployer.ini file but I don’t know, I have the feeling that it would be safer to just find the file without relying on something put there by the OpenText installers. The future will tell if this was the right call. Anyway, so here would be an updated content of the script to automatically choose the Java and run the command (you can also add an additional check to make sure it is indeed a JDK 8 if you want):

[dmadmin@cs-0 scripts]$ cat deploy-all.sh
#!/bin/bash
docbases="GR_REPO1"
dar_list="D2-DAR.dar"
username="dmadmin"
dar_location="$DM_HOME/install/DARsInternal"
password="xxx"

java=`find $DM_HOME/install/composer/ComposerHeadless -type f -name java | head -1`
if [[ ! -x ${java} ]]; then
  java=$JAVA_HOME/bin/java
fi

old_ifs=${IFS}
for docbase in ${docbases}; do
  IFS=','; for dar in ${dar_list}; do
    dar_name=${dar##*/}

    echo "Deploying ${dar_name} into ${docbase}"
    ts=$(date "+%Y%m%d-%H%M%S")

    ${java} -Ddar="${dar_location}/${dar}" \
        -Dlogpath="${dar_location}/dar-deploy-${dar_name}-${docbase}-${ts}.log" \
        -Ddocbase=${docbase} -Duser=${username} -Ddomain= -Dpassword="${password}" \
        -cp $DM_HOME/install/composer/ComposerHeadless/startup.jar \
        org.eclipse.core.launcher.Main \
        -data $DM_HOME/install/composer/workspace \
        -application org.eclipse.ant.core.antRunner \
        -buildfile $DM_HOME/install/composer/deploy.xml

    if [[ ${?} != 0 ]]; then
      echo "ERROR - There was an error while installing the DAR '${dar_name}' into '${docbase}'"
      exit 1
    fi
  done
done
IFS=${old_ifs}
[dmadmin@cs-0 scripts]$
[dmadmin@cs-0 scripts]$ . ./deploy-all.sh
Deploying D2-DAR.dar into GR_REPO1
Buildfile: $DM_HOME/install/composer/deploy.xml

deploy:
[emc.installer] [INFO]  ******************************************************
[emc.installer] [INFO]  * Headless Composer
[emc.installer] [INFO]  * Version:        20.2.0000.0081
[emc.installer] [INFO]  * Java version:   1.8.0_202 (64bit)
[emc.installer] [INFO]  * Java home:      $DM_HOME/install/composer/ComposerHeadless/java/jdk1.8.0_202_x64/jre
[emc.installer] [INFO]  * Set storage type: false
[emc.installer] [INFO]  *
[emc.installer] [INFO]  * DAR file:       $DM_HOME/install/DARsInternal/D2-DAR.dar
[emc.installer] [INFO]  * Project name:   D2-DAR
[emc.installer] [INFO]  * Built by Composer: 7.1.0000.0186
[emc.installer] [INFO]  *
[emc.installer] [INFO]  * Repository:     GR_REPO1
[emc.installer] [INFO]  * Server version: 20.2.0000.0110  Linux64.Postgres
[emc.installer] [INFO]  * User name:      dmadmin
[emc.installer] [INFO]  ******************************************************
[emc.installer] [INFO]  Install started...  Mon Jun 29 00:18:38 UTC 2020
[emc.installer] [INFO]  Executing pre-install script
[emc.installer] [INFO]  dmbasic.exe output : Connected to the server as dmadmin.
...
...
[emc.installer] [INFO]  dmbasic.exe output : Disconnected from the server.
[emc.installer] [INFO]  Finished executing post-install script Mon Jun 29 00:20:40 UTC 2020
[emc.installer] [INFO]  Project 'D2-DAR' was successfully installed.
BUILD SUCCESSFUL

BUILD SUCCESSFUL
Total time: 2 minutes 15 seconds
[dmadmin@cs-0 scripts]$

With this new update of the script, it should work for all versions of Documentum. As mentioned previously, Documentum 20.2 includes the Oracle JDK 8u202 for the Composer Headless. If I’m not mistaken, this is the last free version of the Oracle JDK licensed under the Oracle BCL (Binary Code License). It means that without a Java OTN (Oracle Technology Network) License, you will NOT be able to patch it; it will need to stay in 8u202.

Cet article Documentum – DARs installation fails Java 11 est apparu en premier sur Blog dbi services.

log_duration is a useful point for finding slow running queries and to find performance issues also on the applications side using PostgreSQL as database. Another topic is finding issues with Java Applications using Hibernate after a migration to PostgreSQL. Often Hibernate switches from lazy to eager mode and this has massive impact on the application performance.

In this context I will also describe one of the most useful extensions: pg_stat_statements.

The log duration shown in the logs of PostgreSQL includes the client time, so if you have slow queries it can be also issued by network problems.

For demonstaration I will start with creating my own database:

postgres=# create database blog_log_duration;

After creating the database we leave psql with “\q” and with psql log_log_duration as the default; we connect to our newly created database. The parameter log_duration will switch on logging of the duration for everything and than log_min_duration_statement will show the queries when exeeding the specified runtime.

So both paramters settings, log_duration to on and log_min_duration_statement with a value will fill up the logfile, it makes no sense, so we use log_min_duration_statement only.

postgres=# alter system set log_min_duration_statement = 10000;
ALTER SYSTEM

As an example to log queries runing longer than 10s, the parameter setting is in ms.

postgres=# select pg_reload_conf();
pg_reload_conf
----------------
t
(1 row)

postgres=#

The new setting becomes active as global setting for all databases on this instance. Quitting the postgres connection with “\q” and connecting to our newly created database with:

psql blog_log_duration;

postgres=#select pg_sleep(11);

In the log file we will see the following:

LOG: duration: 11032.666 ms statement: select pg_sleep(11);

Another possibility is to change these settings for one specific database only, for this we need to revoke the global setting with:

postgres=# alter system reset log_min_duration_statement;
ALTER SYSTEM

And reloading the configuration with:

postgres=# select pg_reload_conf();
pg_reload_conf
----------------
t
(1 row)

Checking with:

postgres=# select pg_sleep(11);

… shows no new entry in the log file.

Now we can change this parameter for our test database we created at the beginning:

postgres=# alter database blog_log_duration set log_min_duration_statement = 5000;

Checking for the postgres database:

postgres=# select pg_sleep(11);

… shows again no new entry in the log file.

Settings on database level overruling global settings, just as notice.

Disconnecting from the postgres database with:

postgres=# \q

Connecting to the blog_log_duration database with:

psql blog_log_duration

And checking here with:

blog_log_duration=# select pg_sleep(6);
pg_sleep
----------

(1 row)

blog_log_duration=#

This results in the following line in the log file:

LOG: duration: 6005.967 ms statement: select pg_sleep(6);

Extension pg_stat_statements

This Extension is one of the most useful, it shows what queries have been sent to the database, how often, average, min and max runtime.

For using pg_stat_statements we need to preload libraries, the required configuration can be done with:

postgres=# alter system set shared_preload_libraries = 'pg_stat_statements';

Than a restart is required, a pg_reload_conf(); is not enough.

Then we connect again to our test database with psql blog_log_duration and create the extension with:

blog_log_duration=# create extension pg_stat_statements;
CREATE EXTENSION
blog_log_duration=#

blog_log_duration-# \d pg_stat_statements
View "public.pg_stat_statements"
Column | Type | Collation | Nullable | Default
---------------------+------------------+-----------+----------+---------
userid | oid | | |
dbid | oid | | |
queryid | bigint | | |
query | text | | |
calls | bigint | | |
total_time | double precision | | |
min_time | double precision | | |
max_time | double precision | | |
mean_time | double precision | | |
stddev_time | double precision | | |
rows | bigint | | |
shared_blks_hit | bigint | | |
shared_blks_read | bigint | | |
shared_blks_dirtied | bigint | | |
shared_blks_written | bigint | | |
local_blks_hit | bigint | | |
local_blks_read | bigint | | |
local_blks_dirtied | bigint | | |
local_blks_written | bigint | | |
temp_blks_read | bigint | | |
temp_blks_written | bigint | | |
blk_read_time | double precision | | |
blk_write_time | double precision | | |

blog_log_duration-# ¨

This gives an overview over the view where we can now get the query informations we want to have. This can become very huge, so there are some parameters that can be set to make it more handable.

• pg_stat_statements.max is setting the maximum number of kept queries in this statistic, 1000 for example means the last 1000 queries kept, 5000 is the default.
• pg_stat_statements.track specifies the queries tracked
• pg_stat_statements.track = all tracks nested statements (including statements invoked within functions), none is disabling statement statistics collection and top is tracing top-level statements (those issued directly by clients), the default value is top.
• pg_stat_statements.save specifies if the statistics are saved across shutdowns or restarts, the default is on.

blog_log_duration=# select pg_stat_statements_reset();
pg_stat_statements_reset
--------------------------

(1 row)

blog_log_duration=#

…is resetting the statistics;

Several runs of select pg_sleep();

Both informations are very usefull, showing slow queries is one part, how often they used the other one and this defines the priority where to look at first.

Cet article The log_duration parameter in PostgreSQL est apparu en premier sur Blog dbi services.

I came accross an issue by a customer using aws and terraform. He created a server with ebs volume attached to it but he deleted the volume by mistake.

He then recreated it manually without using the terraform to do it. Thus, the tfstate wasn’t up to date with the new volume and when executing the terraform plan it wanted to create a new volume withe the same name and everything.
So you’ll find the different steps in this blog to re-import the existing volume in the existing terraform tfstate.

We will use terraform in command line directly. I suppose that the path to your tfstate is well set in your .tf file, if you have it localy or in s3 doesn’t matter.

For this blog I’ll use the following resource declarations:
– EBS Volume Resource: aws_ebs_volume.inst-name-volume
– EBS Volume ID: vol-id_of_the_volume
– EBS Attachement Resource: aws_volume_attachment.inst-name-attachement
– Ec2 Instance ID: i-id_of_the_aws_instance

If you execute the plan you’ll find which resource it will try to create:

If the resource names are the same between the ones already in your tfstate and the ones you want to import, you’ll have to remove it from your tfstate as the import cannot update the current configuration.

Here the command to list all your declared resources:

Here the command to remove the desired resources (ebs volume + attachement):

You can now import the existing ebs volume and attachement:

The result of the commands should be successful, if so, you can list the declared resources:

And if you execute the plan again, you should see no change, up to date:

Note that you can do it for an ec2 instance as well simply with:

I hope it helped you, if you have any questions do not hesitate in the comments below.

Cet article Terraform Import from AWS est apparu en premier sur Blog dbi services.

By Franck Pachot

.
The FETCH FIRST … ROWS ONLY syntax arrived in Oracle 12c and is much more convenient than using a subquery with ‘ORDER BY’ wrapped in a “WHERE ROWNUM < …” around it. But as I mentioned in a previous post it required the FIRST_ROWS() hint to get correct estimations. In SQL you don’t want to overload your code for performance, right? The RDBMS optimizer does the job for you. This was a bug with this new FETCH FIRST syntax, that is fixed (See Nigel Bayliss post about this) in 19c:

SQL> select bugno,value,optimizer_feature_enable,description from  V$SYSTEM_FIX_CONTROL where bugno=22174392;

      BUGNO    VALUE    OPTIMIZER_FEATURE_ENABLE                                                      DESCRIPTION
___________ ________ ___________________________ ________________________________________________________________
   22174392        1 19.1.0                      first k row optimization for window function rownum predicate

You can use this query on database metadata to check that you have the fix enabled (VALUE=1 means that the bug is ON). Yes, Oracle Database is not open source, but a lot of information is disclosed: you can query, with SQL, all optimizer enhancements and bug fixes, and versions they appear. And you can even enable or disable them at query level:

select /*+ opt_param('_fix_control' '22174392:OFF') */
continentexp,countriesandterritories,cases from covid where cases>0
order by daterep desc, cases desc fetch first 5 rows only

This simulates previous versions where the fix were not there.

Here is an example on the COVID table I’ve created in a previous post:https://blog.dbi-services.com/oracle-select-from-file/
I’m running this on the Oracle Cloud 20c preview but you can run the same on any recent version.

FETCH FIRST n ROWS

I’m looking at the Top-5 countries with the highest covid cases in the latest date I have in my database. This means ORDER BY the date and number of cases (both in descending order) and fetching only the first 5 rows.

SQL> select continentexp,countriesandterritories,cases
  2  from covid where cases>0
  3  order by daterep desc, cases desc fetch first 5 rows only
  4  /


   CONTINENTEXP     COUNTRIESANDTERRITORIES    CASES
_______________ ___________________________ ________
America         United_States_of_America       57258
Asia            India                          28701
America         Brazil                         24831
Africa          South_Africa                   12058
Europe          Russia                          6615


SQL> select * from dbms_xplan.display_cursor(format=>'allstats last')
  2  /


                                                                                                         PLAN_TABLE_OUTPUT
__________________________________________________________________________________________________________________________
SQL_ID  753q1ymf0sv0w, child number 1
-------------------------------------
select continentexp,countriesandterritories,cases from covid where
cases>0 order by daterep desc, cases desc fetch first 5 rows only

Plan hash value: 1833981741

-----------------------------------------------------------------------------------------------------------------------
| Id  | Operation                | Name  | Starts | E-Rows | A-Rows |   A-Time   | Buffers |  OMem |  1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT         |       |      1 |        |      5 |00:00:00.01 |     239 |       |       |          |
|*  1 |  VIEW                    |       |      1 |      5 |      5 |00:00:00.01 |     239 |       |       |          |
|*  2 |   WINDOW SORT PUSHED RANK|       |      1 |  20267 |      5 |00:00:00.01 |     239 |   124K|   124K|  110K (0)|
|*  3 |    TABLE ACCESS FULL     | COVID |      1 |  20267 |  18150 |00:00:00.01 |     239 |       |       |          |
-----------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("from$_subquery$_002"."rowlimit_$$_rownumber"<=5)
   2 - filter(ROW_NUMBER() OVER ( ORDER BY INTERNAL_FUNCTION("DATEREP") DESC ,INTERNAL_FUNCTION("CASES") DESC )0)

I have queried the execution plan because the RDBMS optimization is not a black box: you can ask for an explanation. Here, it reads the whole table (TABLE ACCESS FULL), SORT it, and FILTER the rows up to number 5.

This is not efficient at all. In a relational database, rather than streaming all changes to another data store, we add purpose-built indexes to scale with a new query use-case:

SQL> create index covid_date_cases on covid(daterep,cases)
  2  /
Index COVID_DATE_CASES created.

That’s all. This index will be automatically maintained with strong consistency, and transparently for any modifications to the table.

NOSORT STOPKEY

I’m running exactly the same query:

SQL> select continentexp,countriesandterritories,cases
  2  from covid where cases>0
  3  order by daterep desc, cases desc fetch first 5 rows only
  4  /

   CONTINENTEXP     COUNTRIESANDTERRITORIES    CASES
_______________ ___________________________ ________
America         United_States_of_America       57258
Asia            India                          28701
America         Brazil                         24831
Africa          South_Africa                   12058
Europe          Russia                          6615

SQL> select * from dbms_xplan.display_cursor(format=>'allstats last')
  2  /

                                                                                              PLAN_TABLE_OUTPUT
_______________________________________________________________________________________________________________
SQL_ID  753q1ymf0sv0w, child number 2
-------------------------------------
select continentexp,countriesandterritories,cases from covid where
cases>0 order by daterep desc, cases desc fetch first 5 rows only

Plan hash value: 1929215041

------------------------------------------------------------------------------------------------------------
| Id  | Operation                     | Name             | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT              |                  |      1 |        |      5 |00:00:00.01 |       7 |
|*  1 |  VIEW                         |                  |      1 |      5 |      5 |00:00:00.01 |       7 |
|*  2 |   WINDOW NOSORT STOPKEY       |                  |      1 |      6 |      5 |00:00:00.01 |       7 |
|   3 |    TABLE ACCESS BY INDEX ROWID| COVID            |      1 |  20267 |      5 |00:00:00.01 |       7 |
|*  4 |     INDEX FULL SCAN DESCENDING| COVID_DATE_CASES |      1 |      6 |      5 |00:00:00.01 |       3 |
------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("from$_subquery$_002"."rowlimit_$$_rownumber"<=5)
   2 - filter(ROW_NUMBER() OVER ( ORDER BY INTERNAL_FUNCTION("DATEREP") DESC,INTERNAL_FUNCTION("CASES") DESC )0)
       filter("CASES">0)

There is a big difference here. I don’t need to read the table anymore. The index provides the entries already sorted and a FULL SCAN DESCENDING will just read the first ones. Look at the ‘Buffer’ column here which is the read units. In the previous test, without the index, it was 239 blocks. But what was bad there is that the FULL TABLE SCAN has a O(N) time complexity. Now with the index, I read only 7 blocks (3 to go down the index B*Tree and 4 to get the remaining column values). And this has a constant time complexity: even with billions of rows in the table this query will read less than 10 blocks, and most of them probably from memory. This will take less than a millisecond whatever the size of the table is.

3 small conclusions here:

• If you think your RDBMS doesn’t scale, be sure that you run the latest version of it. Mainstream database have constant improvement and bug fixes.
• You don’t need another database each time you have another use case. Creating indexes can solve many problems and you have full agility when the RDBMS can create them online, and when there’s zero code to change.
• You don’t need to test on billions of rows. The execution plan operations tell you what scales or not. You don’t need to tell the optimizer how to proceed, but he tells you how he plans and how he did.

Cet article 19c: scalable Top-N queries without further hints to the query planner est apparu en premier sur Blog dbi services.

Over the years I have been working with Documentum, I participated in many migrations and/or upgrades. Just like everything else, this obviously builds up some experience but what if you are pretty new to Documentum and it is your first time working on one? Sure, there is the Documentation from OpenText, which is several dozens of pages (~140, depending on versions) of intense fun so prepare a lot of coffee, you will definitively need some. Except for the documentation, there isn’t much information available so I was thinking about writing a rather short blog to list some key things to absolutely look at if you don’t want to lose all your work or worse. This is obviously not going to be an exhaustive list, it’s not really possible, else it would be in the documentation directly.

The definition of a migration and an upgrade can be found on the documentation. If these two keywords aren’t clear to you, you should definitively go take a look because it can be very confusing, especially some elements of the definition from OpenText. Alright so here are a few key takeaways:

• Read the documentation. Yeah, I know it’s annoying and you will have to excuse me but I had to. There is a lot of crucial information in the documentation, so you don’t really have the choice. This will really help.

• Look at the supported versions early (clients included!). A migration or an upgrade, for Documentum, is a rather complex project and the process that you will need to apply to attain your goal will heavily depend on supported versions. The result will obviously always be the same (the repository is migrated/upgraded) but the path to reach it can be very different. It’s not so easy to define the correct & supported path because there are many possibilities and many things to take into consideration. In addition, there might also be version specific requirements. For example if you are planning to upgrade a Content Server to 16.7 or above, then all DFC Clients (xPlore, DA, D2, …) will also need to be 16.7 or above so this needs to come into the picture.

• Think about the data availability. In the migration/upgrade process, you could opt to keep the source system intact and perform the upgrade on a staging environment before moving to the target system: for example to move from a VM to Docker/Kubernetes. Technically, you don’t need the data on the staging to do an in-place upgrade of the repository, all you need is the Database (export the DB from the source and import it into the DB of the staging). However, performing the in-place upgrade on the staging will create some objects in the repository and these objects will therefore have their data created on the staging data folder. Therefore, if the target system isn’t the staging one, you will then be missing some data because it stayed in the staging while the data that you have on the target is the data from the source (or a copy of the data from the source). If you are following me, you can obviously just perform an additional copy of the staging upgraded data (it’s mainly jar, txt and xml files created by DARs installation), that’s simple because you can easily find which data were created by the upgrade. The purpose of the staging is usually to have the binaries for the upgrade so the initial data will be almost empty, most probably still using the folder “content_storage_01/<hexa_id>/80/00/0x” with x usually equal to 3/4/5. While the data created by the upgrade process will have a much higher id (the next available id, based on the source DB) like “content_storage_01/<hexa_id>/80/8d/6x” for example. I didn’t test it so that might just be a wild guess but maybe re-installing the DARs would have the same effect? That would be something to test…

• Think about encryptions. Whether you are using an AEK key or a Lockbox, you will need to take care about the repository encryption (same for data encryption if you have a TCS license). The simpler is usually to copy the original AEK/Lockbox with its associated repository(ies). However, you might not have this luxury, especially if the source is an old version (AEK needs to be upgraded?).

• Think about passwords (can also be seen as related to the point about encryption). You can change all passwords if you want between the source and the target but that will obviously add an overhead. It’s usually simpler to change passwords (if required) once the migration/upgrade is completed but for that, you will probably want to first copy the AEK/Lockbox. That reminds me of blogs I wrote several years ago about password changes on various Documentum components/layers, like for the Lockbox.

• Think about the Global Registry Repository. In case of migration, the GR doesn’t really need to be migrated, that is only if the Repository that you want to migrate isn’t the GR, obviously ;). However, there might be some data specific for the normal Repository inside the GR, like D2 Keystore information (D2 4.7+) for example. It’s usually faster to just recreate the needed objects/configurations on the target system, compared to the need to duplicate all efforts to migrate another repo (the GR).

• Use the same docbase id. This might sound silly but I prefer to say it, to be sure. If your process involves a different target system, then you will need to install an empty repository on it. It’s not strictly mandatory to use the same docbase id because you can always manually create the needed folder structure on the target system (log folders, data folders, aso…) as well as the needed files (server.ini, dbpasswd.txt, start/stop scripts, ServerApps/ACS config for the repository, aso…). However, doing this manually would take a lot of time to make sure nothing is forgotten while creating the repository, in silent at least, just needs one command to be executed and that’s it. Since you are going to create a repository anyway, you might as well just use directly the correct docbase id from the source. Starting with the CS 7.3, if you want to change the docbase id of a Repository, that’s possible. You don’t have to remove it completely, you can just use the “MigrationUtil” utility (See this blog for an example).

• Make sure there are no locked objects. As far as I remember, the documentation only specify that the dm_server_config objects must not be locked. In reality, you must really check all dm_sysobject. It’s not a problem if some user’s documents are locked since the migration/upgrade process will not update them but Documentum OOTB objects shouldn’t otherwise some steps might fail, even sometimes silently which is then pretty hard to detect. I’m saying this for the dm_ objects but it also applies to other types of objects. For example, if you have a d2_dictionary_archive object locked, then running a D2 Config Import will fail and this is just one of many many cases so better be safe than sorry.

• Look for version specific steps. I already gave an example above about the CS 16.7+ that needs all DFC clients to be 16.7+ as well but there are other things. For example, if you are trying to upgrade to 16.7+ and if you are using a Lockbox, you will first need to extract the AEK Key from the Lockbox since it has been deprecated (See this blog for guidance).

• Verify the components and the logs after. That’s another point that sounds silly but it’s so important… Documentum is a very complex software and there are so many things happening. I have seen so many times things that apparently went well (even according to the main logs) and when you actually start digging into it (looking into Repository objects, looking into sub-logs generated by sub-methods and such), you start seeing a whole new world. Some examples:
  • DARs missing or not installed at all (don’t forget the preserve_existing_types=F during upgrades)
  • Duplicate ACS & JMS objects
  • Lockbox not upgraded (corrupt) (new parameter in 16.4 binaries upgrade)
  • Wrong target_server for the dm_DataDictionaryPublisher job
  • Locked Castor objects due to bug in EBS (introduced in previous patch)
  • JMS or ACS URLs reset to http://localhost
  • JMS that lose its HTTPS configuration
  • aso…

• Stay patient and open-minded. Don’t worry, the migration/upgrade will probably fail but that’s OK, you are here to fix it ;).

These are just some key points I like to keep in mind. If there are some you would like to share, feel free and I can also add them to the list.

Cet article Documentum – Some things to take care of when migrating/upgrading est apparu en premier sur Blog dbi services.

By Franck Pachot

.
J’essaie quelque chose de nouveau. Je publie beaucoup en anglais (blog, articles, présentations) mais cette fois quelque chose de 100% francophone. En sortant du confinement, on reprend les transports (train, voiture,…) et c’est l’occasion de se détendre en musique mais aussi de s’informer avec des podcasts. J’ai l’impression que c’est un format qui a de l’avenir: moins contraignant que regarder une video ou ou lire un article ou une newsletter. Alors je teste une plateforme 100% gratuite: Anchor (c’est un peu le ‘Medium’ du Podcast).

Ce qui me paraît intéressant sur Anchor, c’est qu’il y a une appli smartphone qui permet aussi de laisser des messages vocaux. Alors n’hésitez pas pour des remarques, ou questions. Vos expériences sur les bases de données peuvent être intéressantes pour d’autres. Cloud, migrations Open Source,… c’est dans l’air et c’est toujours utile de partager. Avec l’urgence sanitaire, on voit moins de meetups alors pourquoi pas essayer d’autres media.

Pour le moment j’ai publié 3 épisodes sur Oracle, les sujets importants pour cette année: les Versions (19c ou 20c), les Release Updates et le Multitenant. Et un épisode plus général sur les bases serverless. Les sujets viendront en fonction de l’actualité et de mon expérience quotidienne en consulting, ou recherche. Mais aussi de vos questions.

Anchoe me parait pratique, mais c’est aussi disponible sur Spotify (“Follow” permet d’être notifié des nouveaux épisodes):

Et plusieurs autres platformes, comme iTunes:
https://podcasts.apple.com/ch/podcast/dbpod-le-podcast-bases-de-donn%C3%A9es/id1520397763?l=fr

Ou RadioPublic:

Breaker:
https://www.breaker.audio/db-pod-le-podcast-bases-de-donnees
Google Podcasts:
https://www.google.com/podcasts?feed=aHR0cHM6Ly9hbmNob3IuZm0vcy8yMDdjNmIyMC9wb2RjYXN0L3Jzcw==
Overcast:
https://overcast.fm/itunes1520397763/db-pod-le-podcast-bases-de-donn-es
Pocket Casts:
https://pca.st/qtv36wbn

Pour ces premiers épisodes, je découvre… L’enregistrement est beaucoup trop rapide: j’ai eu la main un peu lourde sur Audacity qui permet d’enlever facilement les imperfections. Et quand on s’écoute soi-même… on en voit partout des imperferctions! N’hésitez pas à me faire un feedback. Sur le fond (les sujets dont vous souhaitez que je parle) et la forme (ça ne peut que s’améliorer…). Et à partager autour de vous, collègues ou managers. Les sujets seront moins techniques et plus généralistes que mes blogs.

Cet article DBPod – le podcast Bases de Données est apparu en premier sur Blog dbi services.

What is Linked server ?

Now a days in each company we have different applications and each one of them have different needs in term of databases support. When data exists on multiple databases the management become a little bit hard. For exemple moving some data from an Oracle database to a SQL Server database is not easy.

A linked servers is configured to enable the Database Engine to execute a Transact-SQL statement that includes tables in another instance of SQL Server, or another database product such as Oracle.

In this Blog, we will see step by step guide to create and configure an Oracle linked server in SQL Server Instance.

• Download ‘oracle database client’

  https://edelivery.oracle.com/osdc/faces/SoftwareDelivery

• Install ‘Oracle database client’

• Create a tnsnames.ora file in (C:\app\client\Administrator\product\12.2\client_1\network\admin)

WSDBA01 =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.106)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SERVICE_NAME = WSDBA01)
    )
  )

• Run powershell as administrator and then do a tnsping
  Check your firewall on each server and between them. In this exemple we do not have any firewall.

• Check your provider by creating a ‘test_connection.udl’ file in your Desktop
  Then double click on it (open it)

• Choose ‘Oracle Provider for OLE DB’ and then click Next

• Enter your service name (defind in tnsnames.ora file) for ‘Data Source’
  Enter a valide username and password and then click on ‘Test Connection’

• Open your SSMS (SQL Server Management Studio) and connect to your SQL Server instance
  Under ‘Server Objects’ then ‘Linked Servers’ and then ‘Providers’ you must see the ‘OraOLEDB.Oracle’

• Right Click on it and then ‘Properties’
  Check mark the ‘Allow inprocess’ and then Click on ‘OK’

• Right click on ‘Linked server’ and then choose ‘New linked server’
• In General section :
  ‘Linked server’ : Give a name to your Linked server
  ‘Provider’ : Choose ‘Oracle Provider for OLE DB’
  ‘Data source’ : Your service name (defined in tnsnames.ora file)

• In Security Section
  Put a valide username and password and then click on ‘OK’

• Now under your Linked server and then ‘Catalogs’ and then ‘default’ your must see every tables that your user have right to query.

enjoy

Cet article Create and configure an Oracle linked server in SQL Server Instance est apparu en premier sur Blog dbi services.

By Franck Pachot

.
Announced by Larry Ellison last week, here it is: the Autonomous Data Guard. You can try it, unfortunately not on the Free Tier.
First you create an Autonomous Database (ATP or ADW) and then you enable Autonomous Data Guard.

You know that “Autonomous” is the marketing brand for the services that automate a lot of things, sometimes based on features that are in Oracle Database for a long time. So let’s see what is behind.

Is it a logical copy?

The slide for the announce mentions that this service maintains a remote copy. That’s right. But the message that it “maintains copy by applying logical changes, not physical changes” is not correct and misleading. What we call “logical changes apply” is logical replication where the changes are transformed to SQL statements and then can be applied to another database that can be a different version, different design,… Like Golden Gate. But Autonomous Data Guard is replicating physical changes. It applies the redo to an exact physical copy of the datafile blocks. Like… a Data Guard physical standby.
But why did Larry Ellison mention “logical” then? Because the apply is at software level. And this is a big difference from storage level synchronisation. We use the term “logical corruption” when a software bug corrupts some data. And we use “physical corruption” when the software write() is ok but the storage write to disk is wrong. And this is why “logical changes” is mentioned there: this software level replication protects from physical corruptions. Data Guard can even detect lost writes between the replicas.
And this is an important message for Oracle because on AWS RDS the standby databases for HA in multi-AZ is at storage level. AWS RDS doesn’t use Data Guard for multi-AZ Oracle. Note that it is different with other databases like Aurora where the changes are written to 6 copies from software redo, Or RDS SQL Server where multi-AZ relies on Always-On.

So, it is not a logical copy but a physical standby database. The point is that it is synchronized by the database software which is more reliable (protects for storage corruption) and more efficient (not all changes need to be replicated and only a few of them must be in sync waiting for the acknowledge).

Is it Autonomous?

Yes, all is automated. The only thing you do is enable it and switchover. Those things are not new. Data Guard was automated in previous versions or the Oracle Database, with the Data Guard Broker, with DBCA creating a standby, with recover from services, and even with automatic failover (FSFO and observer). More than that, “autonomous” means transparent: it happens without service interruption. And that again can be based on many existing features, Application Continuity, Connection Manager Traffic Director,…

So yes it is autonomous and up to a level where the competitors lagging are behind. Currently, AWS application failover is mostly based on DNS changes with all problems coming from caches and timeouts. However, recently, AWS has reduced the gap with AWS RDS Proxy, which is quite new.

This time I totally agree with the term “autonomous”. And I even think it could have been labeled as “serverless” because you don’t see the standby server: you don’t choose the shape, you don’t connect to it. I don’t even see the price but I’ll update this post as soon as I have found it.

Is it Data Guard?

Oh, that’s a great question. And I don’t think we can answer it now. I mentioned many features that can be autonomous, like creating a standby, having a broker to maintain the states, an observer to do the failover,… But that’s all at CDB level in multitenant. However, an Autonomous Database is a PDB. All recovery stuff like redo log shipping is done at CDB level. At least in the current version of it (19c).

However, from the beginning of multitenant, we want to do with a PDB the same things we do with a database. And each release came with more features to look like a standby PDB. Here is a slide I use to illustrate “PDB Switchover”:

So is this Autonomous Data Guard a multitenant feature (refreshable clone) or is it a Data Guard feature? Maybe both.The documentation mentions a RPO of zero for Automatic Failover and a RPO of 5 minutes for manual failover. I don’t think we can have RPO=0 with refreshable clones as the redo is applied with a job that runs every few minutes. So, the automatic failover is probably at CDB level: when the whole CDB is unavailable, as detected by the observer, and standby is in sync, then the standby CDB is activated and all sessions are redirected there (we connect though a Connection Manager). For a manual failover, this must touch only our PDB, and that’s done with a refreshable PDB switchover. They mention RPO=5 minutes because that’s probably to automatic refresh frequency. Then, a manual failover may loose 5 minutes of transactions if the primary is not available. You cannot initiate a failover yourself when the autonomous database is available. When it is available, that’s a switchover without any transaction loss.

So, for the moment in 19c I think that this Autonomous Data Guard is a combination of Data Guard to protect from global failure (failover the whole CDB to another availability domain) and Refreshable PDB for manual failover/switchover. But if you look at the 20c binaries and hidden parameters, you will see more and more mentions of “standby redo logs” and “standby control files” in functions that are related to the PDBs. So you know where it goes: Autonomous means PDB and Autonomous Data Guard will probably push many physical replication features at PDB level. And, once again, when this implementation detail is hidden (do you failover to a CDB standby or a PDB clone?) that deserves a “serverless” hashtag, right? Or should I say that an Autonomous Database is becoming like a CDB-less PDB, where you don’t know in which CDB your PDB is running?

Manual Switchover

Here is my PDB History after a few manual switchovers:

SQL> select * from dba_pdb_history;


                         PDB_NAME    PDB_ID      PDB_DBID                            PDB_GUID     OP_SCNBAS    OP_SCNWRP    OP_TIMESTAMP    OPERATION    DB_VERSION                                                CLONED_FROM_PDB_NAME    CLONED_FROM_PDB_DBID                CLONED_FROM_PDB_GUID    DB_NAME    DB_UNIQUE_NAME       DB_DBID    CLONETAG    DB_VERSION_STRING 
_________________________________ _________ _____________ ___________________________________ _____________ ____________ _______________ ____________ _____________ ___________________________________________________________________ _______________________ ___________________________________ __________ _________________ _____________ ___________ ____________________ 
DWCSSEED                                  3    2852116004 9D288B8436DC5D21E0530F86E50AABD0          1394780            0 27.01.20        CREATE           318767104 PDB$SEED                                                                         1300478808 9D274DFD3CEF1D1EE0530F86E50A3FEF    POD        POD                  1773519138             19.0.0.0.0           
OLTPSEED                                 13     877058107 9EF2060B285F15A5E053FF14000A3E66         14250364            0 19.02.20        CLONE            318767104 DWCSSEED                                                                         2852116004 9D288B8436DC5D21E0530F86E50AABD0    CTRL5      CTRL5                1593803312             19.0.0.0.0           
OLTPSEED_COPY                             4    3032004105 AA768E27A41904D5E053FF14000A4647         34839618            0 15.07.20        CLONE            318767104 OLTPSEED                                                                          877058107 9EF2060B285F15A5E053FF14000A3E66    CTRL5      CTRL5                1593803312             19.0.0.0.0           
OLTPSEED_COPY                             4    3032004105 AA768E27A41904D5E053FF14000A4647         34841402            0 15.07.20        UNPLUG           318767104                                                                                           0                                     CTRL5      CTRL5                1593803312             19.0.0.0.0           
POOLTENANT_OLTPSEED21594803198          289    3780898157 AA780E2370A0AB9AE053DB10000A1A31       3680404503         8559 15.07.20        PLUG             318767104 POOLTENANT_OLTPSEED21594803198                                                   3032004105 AA768E27A41904D5E053FF14000A4647    E3Z1POD    e3z1pod              1240006038             19.0.0.0.0           
CQWRIAXKGYBKVNX_DB202007151508          289    3780898157 AA780E2370A0AB9AE053DB10000A1A31       3864706491         8559 15.07.20        RENAME           318767104 POOLTENANT_OLTPSEED21594803198                                                   3780898157 AA780E2370A0AB9AE053DB10000A1A31    E3Z1POD    e3z1pod              1240006038             19.0.0.0.0           
CQWRIAXKGYBKVNX_DB202007151508          231    1129302642 AA780E2370A0AB9AE053DB10000A1A31       3877635830         8559 15.07.20        CLONE            318767104 CQWRIAXKGYBKVNX_DB202007151508@POD_CDB_ADMIN$_TEMPDBL_PCOUV6FR5J                 3780898157 AA780E2370A0AB9AE053DB10000A1A31    EKG1POD    ekg1pod               918449036             19.0.0.0.0           
CQWRIAXKGYBKVNX_DB202007151508          336    1353046666 AA780E2370A0AB9AE053DB10000A1A31       4062625844         8559 15.07.20        CLONE            318767104 CQWRIAXKGYBKVNX_DB202007151508@POD_CDB_ADMIN$_TEMPDBL_LXW8COMBRV                 3780898157 AA780E2370A0AB9AE053DB10000A1A31    E3Z1POD    e3z1pod              1240006038             19.0.0.0.0           
CQWRIAXKGYBKVNX_DB202007151508          258    1792891716 AA780E2370A0AB9AE053DB10000A1A31       4090531039         8559 15.07.20        CLONE            318767104 CQWRIAXKGYBKVNX_DB202007151508@POD_CDB_ADMIN$_TEMPDBL_YJSIBZ76EE                 3780898157 AA780E2370A0AB9AE053DB10000A1A31    EKG1POD    ekg1pod               918449036             19.0.0.0.0           
CQWRIAXKGYBKVNX_DB202007151508          353    2591868894 AA780E2370A0AB9AE053DB10000A1A31       4138073371         8559 15.07.20        CLONE            318767104 CQWRIAXKGYBKVNX_DB202007151508@POD_CDB_ADMIN$_TEMPDBL_LJ47TUYFEX                 3780898157 AA780E2370A0AB9AE053DB10000A1A31    E3Z1POD    e3z1pod              1240006038             19.0.0.0.0           


10 rows selected. 

You see the switchover as a ‘CLONE’ operation. A clone with the same GUID. The primary was the PDB_DBID=1792891716 that was CON_ID=258 in its CDB. And the refreshable clone PDB_DBID=2591868894 opened as CON_ID=353 is the one I switched over, which is now the primary.

I have selected from DBA_PDBS as json-formatted (easy in SQLcl) to show the columns in lines:

{
          "pdb_id" : 353,
          "pdb_name" : "CQWRIAXKGYBKVNX_DB202007151508",
          "dbid" : 3780898157,
          "con_uid" : 2591868894,
          "guid" : "AA780E2370A0AB9AE053DB10000A1A31",
          "status" : "NORMAL",
          "creation_scn" : 36764763159835,
          "vsn" : 318767104,
          "logging" : "LOGGING",
          "force_logging" : "NO",
          "force_nologging" : "NO",
          "application_root" : "NO",
          "application_pdb" : "NO",
          "application_seed" : "NO",
          "application_root_con_id" : "",
          "is_proxy_pdb" : "NO",
          "con_id" : 353,
          "upgrade_priority" : "",
          "application_clone" : "NO",
          "foreign_cdb_dbid" : 918449036,
          "unplug_scn" : 36764717154894,
          "foreign_pdb_id" : 258,
          "creation_time" : "15.07.20",
          "refresh_mode" : "NONE",
          "refresh_interval" : "",
          "template" : "NO",
          "last_refresh_scn" : 36764763159835,
          "tenant_id" : "(DESCRIPTION=(TIME=1594839531009)(TENANT_ID=29A6A11B6ACD423CA87B77E1B2C53120,29A6A11B6ACD423CA87B77E1B2C53120.53633434F47346E29EE180E736504429))",
          "snapshot_mode" : "MANUAL",
          "snapshot_interval" : "",
          "credential_name" : "",
          "last_refresh_time" : "15.07.20",
          "cloud_identity" : "{\n  \"DATABASE_NAME\" : \"DB202007151508\",\n  \"REGION\" : \"us-ashburn-1\",\n  \"TENANT_OCID\" : \"OCID1.TENANCY.OC1..AAAAAAAACVSEDMDAKDVTTCMGVFZS5RPB6RTQ4MCQBMCTZCVCR2NWDUPYLYEQ\",\n  \"DATABASE_OCID\" : \"OCID1.AUTONOMOUSDATABASE.OC1.IAD.ABUWCLJSPZJCV2KUXYYEVTOZSX7K5TXGYOHXMIGWUXN47YPGVSAFEJM3SG2A\",\n  \"COMPARTMENT_OCID\" : \"ocid1.tenancy.oc1..aaaaaaaacvsedmdakdvttcmgvfzs5rpb6rtq4mcqbmctzcvcr2nwdupylyeq\",\n  \"OUTBOUND_IP_ADDRESS\" :\n  [\n    \"150.136.133.92\"\n  ]\n}"
        }

You can see, from the LAST_REFRESH_SCN equal to the CREATION_SCN, that the latest committed transactions were synced at the time of the switchover: the ATP service shows: “Primary database switchover completed. No data loss during transition!”

And here is the result from the same query before the switchover (I display only what had changed):

          "pdb_id" : 258,
          "con_uid" : 1792891716,
          "creation_scn" : 36764715617503,
          "con_id" : 258,
	  "foreign_cdb_dbid" : 1240006038,
          "unplug_scn" : 36764689231834,
          "foreign_pdb_id" : 336,
          "last_refresh_scn" : 36764715617503,
          "tenant_id" : "(DESCRIPTION=(TIME=1594835734415)(TENANT_ID=29A6A11B6ACD423CA87B77E1B2C53120,29A6A11B6ACD423CA87B77E1B2C53120.53633434F47346E29EE180E736504429))",

PDB_ID and CON_ID were different because plugged in a different CDB. But DBID and GUID are the same on the primary and the clone because it is the same datafile content. The FOREIGN_CDB_DBID and FOREIGN_PDB_ID is what references the primary from the standby and the standby from the primary. The LAST_REFRESH_SCN is always equal to the CREATION_SCN, when I query it from the primary, as it was activated without data loss. I cannot query the refreshable clone when it is in standby role.

Autonomous and Serverless doesn’t mean Traceless, fortunately:

SQL> select payloadfrom GV$DIAG_TRACE_FILE_CONTENTS where TRACE_FILENAME in ('e3z1pod4_ora_108645.trc') order by timestamp;   

PAYLOAD
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
*** 2020-07-15T18:33:16.885602+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Started Serial Media Recovery
Loading kcnibr for container 353
Dumping database incarnation table:
Resetlogs 0 scn and time: 0x00000000001df6a8 04/23/2020 20:44:09
Dumping PDB pathvec - index 0
   0000 : pdb 353, dbinc 3, pdbinc 0
          db rls 0x00000000001df6a8 rlc 1038516249
          incscn 0x0000000000000000 ts 0
          br scn 0x0000000000000000 ts 0
          er scn 0x0000000000000000 ts 0
   0001 : pdb 353, dbinc 2, pdbinc 0
          db rls 0x00000000001db108 rlc 1038516090
          incscn 0x0000000000000000 ts 0
          br scn 0x0000000000000000 ts 0
          er scn 0x0000000000000000 ts 0
Recovery target incarnation = 3, activation ID = 0
Influx buffer limit = 100000 min(50% x 29904690, 100000)
Start recovery at thread 7 ckpt scn 36764741795405 logseq 0 block 0
*** 2020-07-15T18:33:17.181814+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 7
*** 2020-07-15T18:33:17.228175+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 1
*** 2020-07-15T18:33:17.273432+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 2
*** 2020-07-15T18:33:17.318517+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 3
*** 2020-07-15T18:33:17.363512+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 4
*** 2020-07-15T18:33:17.412186+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 5
*** 2020-07-15T18:33:17.460044+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 6
*** 2020-07-15T18:33:17.502354+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery add redo thread 8
*** 2020-07-15T18:33:17.575400+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_7_2609_1_1035414033.arc
krr_open_logfile: Restricting nab of log-/u02/nfsad1/e19pod/parlog_7_2609_1_1035414033.arc, thr-7, seq-2609                to 2 blocks.recover pdbid-258
*** 2020-07-15T18:33:17.620308+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_1_2610_1_1035414033.arc
Generating fake header for thr-1, seq-2610
*** 2020-07-15T18:33:17.651042+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_2_2604_1_1035414033.arc
krr_open_logfile: restrict nab of remote log with                  thr#-2, seq#-2604, file-/u02/nfsad1/e19pod/parlog_2_2604_1_1035414033.arc, kcrfhhnab-43080320, newnab-43080320
*** 2020-07-15T18:33:41.867605+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_3_2696_1_1035414033.arc
Generating fake header for thr-3, seq-2696
*** 2020-07-15T18:33:41.900123+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_4_2585_1_1035414033.arc
Generating fake header for thr-4, seq-2585
*** 2020-07-15T18:33:41.931004+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_5_2967_1_1035414033.arc
Generating fake header for thr-5, seq-2967
*** 2020-07-15T18:33:41.963625+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_6_2611_1_1035414033.arc
Generating fake header for thr-6, seq-2611
*** 2020-07-15T18:33:41.998296+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery Log /u02/nfsad1/e19pod/parlog_8_2586_1_1035414033.arc
Generating fake header for thr-8, seq-2586
*** 2020-07-15T18:33:53.033726+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 8
*** 2020-07-15T18:33:53.033871+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 6
*** 2020-07-15T18:33:53.033946+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 5
*** 2020-07-15T18:33:53.034015+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 4
*** 2020-07-15T18:33:53.034154+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 3
*** 2020-07-15T18:33:53.034239+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 1
*** 2020-07-15T18:33:53.034318+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 7
==== Redo read statistics for thread 2 ====
Total physical reads (from disk and memory): 21540159Kb
-- Redo read_disk statistics --
Read rate (ASYNC): 21540159Kb in 35.77s => 588.07 Mb/sec
Total redo bytes: 21540159Kb Longest record: 12Kb, moves: 20988/2785829 moved: 179Mb (0%)
Longest LWN: 31106Kb, reads: 5758
Last redo scn: 0x0000216ff58a3d72 (36764744564082)
Change vector header moves = 264262/2971514 (8%)
----------------------------------------------
*** 2020-07-15T18:33:53.034425+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Media Recovery drop redo thread 2
KCBR: Number of read descriptors = 1024
KCBR: Media recovery blocks read (ASYNC) = 77
KCBR: Influx buffers flushed = 9 times
KCBR: Reads = 2 reaps (1 null, 0 wait), 1 all
KCBR: Redo cache copies/changes = 667/667
*** 2020-07-15T18:33:53.187031+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
Completed Media Recovery
----- Abridged Call Stack Trace -----
ksedsts()+426<-krdsod()+251<-kss_del_cb()+218<-kssdel()+216<-krdemr()+5836<-krd_end_rcv()+609<-dbs_do_recovery()+3232<-dbs_rcv_start_main()+4890<-dbs_rcv_start()+115<-kpdbcRecoverPdb()+1039<-kpdbSwitch()+3585<-kpdbcApplyRecovery()+2345<-kpdbcRefreshPDB()+12073<-kpdbSwitchRunAsSysCbk()+20<-rpiswu2()+2004<-kpdbSwitch()+3563<-kpdbcRefreshDrv()+1410<-kpdbSwitch()+3585<-kpdbadrv()+34922<-opiexe()+26658<-opiosq0()+4635<-opipls()+14388<-opiodr()+1202<-rpidrus()+198<-skgmstack()+65<-rpidru()+132<-rpiswu2()+543<-rpidrv()+1266
*** 2020-07-15T18:33:53.252481+00:00 (CQWRIAXKGYBKVNX_DB202007151508(353))
<-psddr0()+467<-psdnal()+624<-pevm_EXIM()+282<-pfrinstr_EXIM()+43<-pfrrun_no_tool()+60<-pfrrun()+902<-plsql_run()+755<-peicnt()+279<-kkxexe()+720<-opiexe()+31050<-kpoal8()+2226<-opiodr()+1202<-ttcpip()+1239<-opitsk()+1897<-opiino()+936<-opiodr()+1202<-opidrv()+1094
<-sou2o()+165<-opimai_real()+422<-ssthrdmain()+417<-main()+256<-__libc_start_main()+245
----- End of Abridged Call Stack Trace -----
Partial short call stack signature: 0x43b703b8697309f4
Unloading kcnibr
Elapsed: 01:00:03.376

Looking at the call stack (kpdbcRecoverPdb<-kpdbSwitch<-kpdbcApplyRecovery<-kpdbcRefreshPDB<-kpdbSwitchRunAsSysCbk<-rpiswu2<-kpdbSwitch<-kpdbcRefreshDrv<-kpdbSwitch) it is clear that Autonomous Data Guard manual switchover is nothing else than a "Refreshable PDB Switchover", feature introduced in 18c and available only on Oracle Engineered Systems (Exadata and ODA) and Oracle Cloud. At least for the moment.

Cet article A Serverless Standby Database called Oracle Autonomous Data Guard est apparu en premier sur Blog dbi services.

Introduction

Before the freshly come “workload manager”  feature on latest Control-M versions, the Control-M users used a lot of workarounds to manage the workload execution.

Using Quantitative resources was one of the most used.

Request

We need to trigger a workflow on demand without having to hold the jobs or release them manually.

For example, launch it and stop it at specifics time (on demand).
Or preventing side effect if an operation that can impact the application is scheduled (holding the workflow then release it)

Solution

Create 2 jobs updating quantitative resources for the application (workflow) we want to trigger.

Quantitative resource creation

Definition

A quantitative resource represents a measure that can be quantified such as percentage of CPU, megabytes of storage, or number of tape drives. It provides the ability to avoid overwhelming the physical and logical resources in an environment by limiting the number of jobs that use the same resource at the same time.

Cmdline method

Using ecaqrtab utility to list the existing QR:
Under control user :

CTMSRVCENTOS% ecaqrtab list

Date: 15-Jun-2020.   Page: 1




Quantitative resource list




+-------------------------------------------------------------------------------------------------+

Resource Name                                                       Max-Avail  Reserved Used Free

+-------------------------------------------------------------------------------------------------+

Using ecaqrtab utility to create your QR (here named QRSTOP):

CTMSRVCENTOS%

CTMSRVCENTOS% ecaqrtab ADD QRSTOP




Total :99

Quantitative resource 'QRSTOP', Max availability '99' was added.

CTMSRVCENTOS%

Check if QR is created :

CTMSRVCENTOS% ecaqrtab LIST
Date: 17-Jun-2020.   Page: 1

Quantitative resource list

+-------------------------------------------------------------------------------------------------+
 Resource Name                                                       Max-Avail  Reserved Used Free
+-------------------------------------------------------------------------------------------------+
 QRSTOP                                                              99         0        0    99

CTMSRVCENTOS%

Using GUI method

By selecting tools in monitoring pane:

Click on add resource and define resource name Control-M server name and maximum resources you want to allocate.

Note

If you did the cmdline method, your resource will be displayed as well in QR( quantitative resource )  part.

This first step done; we will assign the jobs which will be managed by this resource.

QR allocation

Affect to all job by find and update method ( see my previous topic ) the QR created above. ( QRSTOP )

Each job must need 1 QR to be submitted.

The aim is to switch the maximum QR from 99 to 0 in order to block the workflow.

Starting from that it will be easy to manage when this application can be triggered.

Assigning QR to your workflow

For our example I will create an Application composed by jobs that will depend of QR.

I will use the mass create option to create 10 jobs with QR assigned:

Note

Ton increment the jobs you can use the syntax JOBNAME{Counter} don’t forget the Uppercase for “C”or it will not work

To assign the QR to the jobs , add it to prerequisites part with the quantity needed and the total amount (here, 1 QR per job and total amount 99 )

Use jobs to update QR

Now we have all jobs depending of the CR we will create 2 jobs: 1 that update QR to 99 and another that update QR to 0 (which will block the workflow)

Command to use in the job will be

To update Quantitative resource ‘QRSTOP’ to 99:

CTMSRVCENTOS% ecaqrtab UPDATE QRSTOP 99

Quantitative resource 'QRSTOP', was updated from '0' to '99'

To reset the Quantitative resource ‘QRSTOP’ to 0:

CTMSRVCENTOS% ecaqrtab UPDATE QRSTOP 0

Quantitative resource 'QRSTOP', was updated from '99' to '0'.

For more security you can configure your QR jobs to be launched manually (or define a specific   time to start)

We can see that jobs are waiting for the QR that we defined (QRSTOP) as for the moment total amount is 0.

To submit these jobs, all that remains to be done is to release the job JOB_TEST_QR_TO_99

Result

The jobs are submitted as expected:

To stop the workflow, we can start run the JOB_TEST_QR_TO_0.
This will reset the QR in order to stop the workflow.
 

Note

Now you can set as you want the execution time of your “QR manager” : JOB_TEST_QR_TO_0 and JOB_TEST_QR_TO_99.
Depending of your need you can modulate it

Example

Configure the QR job JOB_TEST_QR_TO_99 to be submitted at 08h00 then define the QR job JOB_TEST_QR_TO_0  to be scheduled at 19h00.

Conclusion

This method can be used on any Control-M version, but now with the new feature Control-M workload manager you have way more option to configure your workflow.
For next topics we will check another method to schedule your applications at specifics times.
Feel free to check dbi’s bloggers many interesting subject on Control -M , database and many other technologies!

Cet article Control-M/EM : How to manage a workflow with ecaqrtab utility est apparu en premier sur Blog dbi services.