Creating a snapshopt copy Pluggable Database (PDB) on top of Automatic Storage Management (ASM) is not possible, because you need to have a filesystem which supports sparse files. According the following MOS-Note sparse files are supported on Automatic Storage Management Cluster File System (ACFS) since 12.2.:
12.2 Oracle ACFS Sparse Files Enhancements (Doc ID 2200264.1)
However, I thought it is more fun to create a PDB Snapshot Copy on a XFS-filesystem, which I wanted to create as a 3rd party filesystem on top of Oracle ASM Dynamic Volume Manager (ADVM) volumes.
REMARK1: See the steps at the end of this Blog on how to create a PDB Snapshot Copy on top of ACFS.
REMARK2: All tests have been done on the Oracle Cloud with a DB system running as a VM.
Here’s what I did:
1. Create a XFS-filesystem of size 20G on ASM diskgroup DATA
Create the volume MYXFSVOL on diskgroup DATA as grid:
grid@cbl:/home/grid/ [+ASM1] asmcmd volcreate -G DATA -s 20g MYXFSVOL grid@cbl:/home/grid/ [+ASM1] asmcmd volinfo --all Diskgroup Name: DATA Volume Name: MYXFSVOL Volume Device: /dev/asm/myxfsvol-187 State: ENABLED Size (MB): 20480 Resize Unit (MB): 64 Redundancy: UNPROT Stripe Columns: 8 Stripe Width (K): 1024 Usage: Mountpath:
Create the xfs-filesystem as root:
[root@cbl ~]# mkdir /u01/app/oracle/myxfs
[root@cbl ~]# mkfs.xfs /dev/asm/myxfsvol-187
meta-data=/dev/asm/myxfsvol-187 isize=256 agcount=4, agsize=1310720 blks
= sectsz=4096 attr=2, projid32bit=1
= crc=0 finobt=0, sparse=0
data = bsize=4096 blocks=5242880, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=4096 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@cbl ~]# mount -t xfs /dev/asm/myxfsvol-187 /u01/app/oracle/myxfs
[root@cbl ~]# chown oracle:oinstall /u01/app/oracle/myxfs
2. Prepare the CDB for Snapshot Copy
SQL> connect / as sysdba Connected. SQL> show parameter clonedb NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ clonedb boolean FALSE clonedb_dir string SQL> alter system set clonedb=true scope=spfile; System altered.
and restart the DB:
oracle@cbl:/home/oracle/ [DB0111 (CDB$ROOT)] srvctl stop database -db DB0111_zrh13m oracle@cbl:/home/oracle/ [DB0111 (CDB$ROOT)] srvctl start database -db DB0111_zrh13m
3. Create a PDB as a Read-Only master for the Snapshot Copy
SQL> create pluggable database pdb2 admin user pdbadmin identified by "manager"; Pluggable database created. SQL> alter pluggable database pdb2 open; Pluggable database altered. SQL> alter session set container=pdb2; Session altered. SQL> create user cbleile identified by "in_reality_I_used_something_different"; User created. SQL> grant connect, resource, dba to cbleile; Grant succeeded. SQL> create table cbleile.t1 (n number, m varchar2(100)); Table created. SQL> insert into cbleile.t1 values (1,'Before Snapshot Copy created'); 1 row created. SQL> commit; Commit complete. SQL> connect / as sysdba Connected. SQL> alter pluggable database pdb2 close immediate; Pluggable database altered. SQL> alter pluggable database pdb2 open read only; Pluggable database altered.
Here the file names of my read-only opened PDB:
SQL> select file_name from cdb_data_files where con_id=5; FILE_NAME ------------------------------------------------------------------------------------------- +DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/system.288.1077982211 +DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/sysaux.289.1077982211 +DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1.287.1077982211 +DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211
4. Create the Snapshot Copy:
SQL> create pluggable database pdb2sc from pdb2 snapshot copy file_name_convert=('+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF','/u01/app/oracle/myxfs');
create pluggable database pdb2sc from pdb2 snapshot copy file_name_convert=('+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF','/u01/app/oracle/myxfs')
*
ERROR at line 1:
ORA-65169: error encountered while attempting to copy file
+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211
ORA-17515: Creation of clonedb failed using snapshot file
+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211
ORA-17637: failed to change permission on file
'+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211'
ORA-15304: operation requires ACCESS_CONTROL.ENABLED attribute to be TRUE
So obviously Oracle tried to set the files of the read only started PDB PDB2 explicitely to read only on ASM-level.
OK, let’s enable ACCESS_CONTROL:
grid@cbl:/home/grid/ [+ASM1] asmcmd ASMCMD> setattr -G DATA access_control.enabled TRUE
It still doesn’t work, but now I get a permission denied error:
SQL> create pluggable database pdb2sc from pdb2 snapshot copy file_name_convert=('+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF','/u01/app/oracle/myxfs');
create pluggable database pdb2sc from pdb2 snapshot copy file_name_convert=('+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF','/u01/app/oracle/myxfs')
*
ERROR at line 1:
ORA-65169: error encountered while attempting to copy file
+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211
ORA-17515: Creation of clonedb failed using snapshot file
+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211
ORA-17637: failed to change permission on file
'+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE/undotbs1_temp.286.1077982211'
ORA-15260: permission denied on ASM disk group
ASMCMD> pwd
+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF/DATAFILE
ASMCMD> ls --permission
User Group Permission Name
rw-rw-rw- SYSAUX.289.1077982211
rw-rw-rw- SYSTEM.288.1077982211
rw-rw-rw- UNDOTBS1.287.1077982211
rw-rw-rw- UNDOTBS1_TEMP.286.1077982211
So I have to create the User oracle in ASM for diskgroup DATA:
ASMCMD> mkusr DATA oracle
And then set the owner of the PDB2-datafiles to oracle:
ASMCMD> chown oracle SYSAUX.289.1077982211 SYSTEM.288.1077982211 UNDOTBS1.287.1077982211 UNDOTBS1_TEMP.286.1077982211 ASMCMD> ls --permission User Group Permission Name oracle@0a5d56d4388b4f7bbf6da84da547ae9e rw-rw-rw- SYSAUX.289.1077982211 oracle@0a5d56d4388b4f7bbf6da84da547ae9e rw-rw-rw- SYSTEM.288.1077982211 oracle@0a5d56d4388b4f7bbf6da84da547ae9e rw-rw-rw- UNDOTBS1.287.1077982211 oracle@0a5d56d4388b4f7bbf6da84da547ae9e rw-rw-rw- UNDOTBS1_TEMP.286.1077982211 ASMCMD>
Let’s do it for the tempfile as well:
ASMCMD> cd ../TEMPFILE ASMCMD> ls TEMP.290.1077982223 ASMCMD> chown oracle TEMP.290.1077982223 ASMCMD> ls --permission User Group Permission Name oracle@0a5d56d4388b4f7bbf6da84da547ae9e rw-rw-rw- TEMP.290.1077982223 ASMCMD>
Finally I just created the necessesary folders:
SQL> !mkdir /u01/app/oracle/myxfs/DATAFILE/ SQL> !mkdir /u01/app/oracle/myxfs/TEMPFILE/
And now it worked:
SQL> create pluggable database pdb2sc from pdb2 snapshot copy file_name_convert=('+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF','/u01/app/oracle/myxfs');
Pluggable database created.
SQL> alter pluggable database PDB2SC open;
Pluggable database altered.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 PDB1 READ WRITE NO
5 PDB2 READ ONLY NO
6 PDB2SC READ WRITE NO
That looks promising. Let’s try it:
SQL> alter session set container=PDB2SC;
Session altered.
SQL> set lines 200 pages 999
SQL> column m format a32
SQL> select * from cbleile.t1;
N M
---------- --------------------------------
1 Before Snapshot Copy created
SQL>
SQL> column file_name format a70
SQL> select file_name from dba_data_files;
FILE_NAME
----------------------------------------------------------------------
/u01/app/oracle/myxfs/DATAFILE/system.288.1077982211
/u01/app/oracle/myxfs/DATAFILE/sysaux.289.1077982211
/u01/app/oracle/myxfs/DATAFILE/undotbs1.287.1077982211
/u01/app/oracle/myxfs/DATAFILE/undotbs1_temp.286.1077982211
SQL>
SQL> !ls -lhs /u01/app/oracle/myxfs/DATAFILE
total 196K
116K -rw-r----- 1 oracle asmadmin 401M Jul 15 16:02 sysaux.289.1077982211
48K -rw-r----- 1 oracle asmadmin 291M Jul 15 16:02 system.288.1077982211
16K -rw-r----- 1 oracle asmadmin 46M Jul 15 16:02 undotbs1.287.1077982211
16K -rw-r----- 1 oracle asmadmin 3.2M Jul 15 16:02 undotbs1_temp.286.1077982211
SQL>
–> Cool, the files are only a couple of KB in size.
SQL> insert into cbleile.t1 values (2,'After creating the Snapshot Copy');
1 row created.
SQL> commit;
Commit complete.
SQL> select * from cbleile.t1;
N M
---------- --------------------------------
1 Before Snapshot Copy created
2 After creating the Snapshot Copy
SQL>
Summary: You can create a Snapshot Copy Pluggable Database on top of ASM by using a filesystem which supports sparse files. If your read-only source-PDB is on ASM then you have to enable access control in ASM and set oracle as the owner of the datafiles of the read-only source-PDB.
REMARK: Above tests with XFS have been done on a single instance setup. Running your CDB in RAC then ACFS as the filesystem for the Snapshot Copy PDB should to be used.
For completness below the steps to create the Snapshot Copy on top of ACFS (as I used the same Read-Only source-PDB, I didn’t have to set permissions again):
grid@cbl:/home/grid/ [+ASM1] asmcmd volcreate -G DATA -s 20g MYACFSVOL
grid@cbl:/home/grid/ [+ASM1] asmcmd volinfo --all
Diskgroup Name: DATA
Volume Name: MYACFSVOL
Volume Device: /dev/asm/myacfsvol-187
State: ENABLED
Size (MB): 20480
Resize Unit (MB): 64
Redundancy: UNPROT
Stripe Columns: 8
Stripe Width (K): 1024
Usage:
Mountpath:
grid@cbl:/home/grid/ [+ASM1]
[root@cbl ~]# mkdir /u01/app/oracle/myacfs
[root@cbl ~]# mkfs.acfs /dev/asm/myacfsvol-187
mkfs.acfs: version = 21.0.0.0.0
mkfs.acfs: on-disk version = 50.0
mkfs.acfs: volume = /dev/asm/myacfsvol-187
mkfs.acfs: volume size = 21474836480 ( 20.00 GB )
mkfs.acfs: file system size = 21474836480 ( 20.00 GB )
mkfs.acfs: Format complete.
[root@cbl ~]#
[root@cbl ~]# mount -t acfs /dev/asm/myacfsvol-187 /u01/app/oracle/myacfs
[root@cbl ~]# chown oracle:oinstall /u01/app/oracle/myacfs
oracle@cbl:/home/oracle/ [DB0111 (CDB$ROOT)] sqlplus / as sysdba
SQL> !ls -l /u01/app/oracle/myacfs
total 64
drwx------ 2 root root 65536 Jul 15 17:30 lost+found
SQL> !mkdir /u01/app/oracle/myacfs/DATAFILE
SQL> !mkdir /u01/app/oracle/myacfs/TEMPFILE
SQL> create pluggable database pdb2scacfs from pdb2 snapshot copy file_name_convert=('+DATA/DB0111_ZRH13M/C72C15BBCD038123E0530300000A0FAF','/u01/app/oracle/myacfs');
Pluggable database created.
SQL> alter pluggable database pdb2scacfs open;
Pluggable database altered.
SQL> show pdbs
CON_ID CON_NAME OPEN MODE RESTRICTED
---------- ------------------------------ ---------- ----------
2 PDB$SEED READ ONLY NO
3 PDB1 READ WRITE NO
4 PDB2SCACFS READ WRITE NO
5 PDB2 READ ONLY NO
6 PDB2SC READ WRITE NO
SQL> !ls -lhs /u01/app/oracle/myacfs/DATAFILE
total 208K
116K -rw-r----- 1 oracle asmadmin 401M Jul 15 17:34 sysaux.289.1077982211
52K -rw-r----- 1 oracle asmadmin 291M Jul 15 17:34 system.288.1077982211
20K -rw-r----- 1 oracle asmadmin 46M Jul 15 17:34 undotbs1.287.1077982211
20K -rw-r----- 1 oracle asmadmin 3.2M Jul 15 17:34 undotbs1_temp.286.1077982211
SQL> alter session set container=PDB2SCACFS;
Session altered.
SQL> set lines 200 pages 999
SQL> column m format a50
SQL> select * from cbleile.t1;
N M
---------- --------------------------------------------------
1 Before Snapshot Copy created
SQL> insert into cbleile.t1 values (2,'After creating a Snapshot Copy on top of ACFS');
1 row created.
SQL> commit;
Commit complete.
SQL> select * from cbleile.t1;
N M
---------- --------------------------------------------------
1 Before Snapshot Copy created
2 After creating a Snapshot Copy on top of ACFS
SQL>
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