cloning


CloneDB: terminating the instance due to error 17514

While getting adventureous and trying to enable clonedb on a RAC database running on ASM (set clonedb parameter=true and restart the database), I got this error on alert log:

Mon Nov 16 11:11:40 2015
CloneDB: created bitmap file RAC_bitmap.dbf
USER (ospid: 15767): terminating the instance due to error 17514

RAC is the name of the database. The <SID>_bitmap.dbf file was correctly created on $ORACLE_HOME/dbs

Then it just crash the instance. Google and Metalink did not yet indexed this error. But here its description:


$ oerr ora 17514
17514, 00000, "Access to clonedb bitmap file failed"
// *Cause: Accessing the bitmap block file in clonedb environment has
// encountered an error
// *Action: check additional error messages in the trace file and call
// Oracle Support Services

The trace files did not help much. I did not investigate the problem further.


Thin PDB clones on ext4 filesystem with Oracle 12.1.0.2

Oracle 12.1.0.2 brings a great new functionality: you can create thin clones – that is, not copying the source files, just pointers – on ext4 filesystem, the current default on Red Hat Linux 6.

Requirements for example below:
– Oracle 12.1.0.2
– Data files are on ext4 filesystem (or other supporting sparse files)
– Source PDB on read only mode

It is very simple to set up:

SQL> alter system set clonedb=TRUE scope=spfile;
SQL> shutdown immediate
SQL> startup

SQL> show parameter clonedb
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
clonedb                              boolean     TRUE

I will create a clone of the PDB2 database.

SQL> select name,con_id,open_mode,SNAPSHOT_PARENT_CON_ID from v$pdbs;

NAME                               CON_ID OPEN_MODE  SNAPSHOT_PARENT_CON_ID
------------------------------ ---------- ---------- ----------------------
PDB$SEED                                2 READ ONLY                       0
PDB1                                    3 MOUNTED                         0
PDB2                                    4 READ ONLY                       0

For this I need first to create the target directory for the datafiles.

SQL> ! mkdir -p /u01/app/oracle/oradata/NONRAC/PDB2_CLONE1

Then I can do the clone using the ‘snapshot copy’ clause. It took 9 seconds.

SQL> create pluggable database PDB2_C1 from PDB2 snapshot copy file_name_convert=('/u01/app/oracle/oradata/NONRAC/PDB2','/u01/app/oracle/oradata/NONRAC/PDB2_CLONE1');
Pluggable database created.

Elapsed: 00:00:09.35

Note that the new PDB remains in MOUNT state and without showing a connection to its parent. I find unfortunate the lack of that information.

SQL> select name,con_id,open_mode,SNAPSHOT_PARENT_CON_ID from v$pdbs;

NAME                               CON_ID OPEN_MODE  SNAPSHOT_PARENT_CON_ID
------------------------------ ---------- ---------- ----------------------
PDB$SEED                                2 READ ONLY                       0
PDB1                                    3 MOUNTED                         0
PDB2                                    4 READ ONLY                       0
PDB2_C1                                 5 MOUNTED                         0

After we open the clone in READ WRITE mode, then we can see the relationship with the parent.

SQL> alter pluggable database PDB2_C1 open read write;
Pluggable database altered.
Elapsed: 00:00:02.12

SQL> select name,con_id,open_mode,SNAPSHOT_PARENT_CON_ID from v$pdbs;

NAME                               CON_ID OPEN_MODE  SNAPSHOT_PARENT_CON_ID
------------------------------ ---------- ---------- ----------------------
PDB$SEED                                2 READ ONLY                       0
PDB1                                    3 MOUNTED                         0
PDB2                                    4 READ ONLY                       0
PDB2_C1                                 5 READ WRITE                      4

And below we verify that the clone uses 4MB instead of 800MB of the source database.

SQL> ! du -m /u01/app/oracle/oradata/NONRAC/PDB2/*
6       /u01/app/oracle/oradata/NONRAC/PDB2/PDB2_users01.dbf
586     /u01/app/oracle/oradata/NONRAC/PDB2/sysaux01.dbf
261     /u01/app/oracle/oradata/NONRAC/PDB2/system01.dbf
1       /u01/app/oracle/oradata/NONRAC/PDB2/temp01.dbf

SQL> ! du -m /u01/app/oracle/oradata/NONRAC/PDB2_CLONE1/*
1       /u01/app/oracle/oradata/NONRAC/PDB2_CLONE1/PDB2_users01.dbf
1       /u01/app/oracle/oradata/NONRAC/PDB2_CLONE1/sysaux01.dbf
1       /u01/app/oracle/oradata/NONRAC/PDB2_CLONE1/system01.dbf
1       /u01/app/oracle/oradata/NONRAC/PDB2_CLONE1/temp01.dbf

We can also clone non-CDB databases with some more steps, as explained at:
https://dbamarco.wordpress.com/2015/03/09/small-change-big-difference/

The clonedb.pl script (see documentation here) can also be used, even though you might find easier to script yourself to your own environment.