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11G New Feature : Enable block change tracking on a physical standby database

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Created on Thursday, 20 October 2011 16:19

Last Updated on Monday, 12 March 2012 13:54

Published on Thursday, 20 October 2011 16:19

Written by Guy Lambregts

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11G New Feature : Enable block change tracking on a physical standby database.

 

Block change tracking is a nice 10G new feature. Changed blocks are tracked in a change tracking file. This is done by a 10G new background process CTWR. This can considerably speed up our incremental backups.
Also interesting is that you can backup your physical standby database and use the backups to recover your primary database ( if needed ).
This is interesting to avoid you primary database server hardware resources are used for your backup in stead off for your business processsing.


Question : Can we use block change tracking to speed up our incremental backups assuming we backup our physical standby databases ?

Answer    : This depends on the release.


Oracle 10G

You can' t use block change tracking on a standby database

You still can use block change tracking on a primary database even if you have a standby databases.
Thus you can still speed up your incremental backup assuming you backup your primary database.


Oracle 11G

You can use block change tracking on both primary databases and standby databases.
Thus you can speed up your incremental backup even when you backup your standby database. ( to offload the primary )


SQL> startup mount;
ORACLE instance started.

Total System Global Area  626327552 bytes
Fixed Size                  2229080 bytes
Variable Size             394267816 bytes
Database Buffers          222298112 bytes
Redo Buffers                7532544 bytes
Database mounted.

SQL> alter database enable block change tracking using file '/opt/oracle/change_tracking_file.ctf';

Database altered.

SQL> select database_role from v$database;

DATABASE_ROLE
----------------
PHYSICAL STANDBY

SQL> select * from v$block_change_tracking;

STATUS
----------
FILENAME
--------------------------------------------------------------------------------
BYTES
----------
ENABLED
/opt/oracle/change_tracking_file.ctf
11599872


SQL> show release;
release 1102000200.

What is the alert file telling us ?


Media Recovery Waiting for thread 1 sequence 331 (in transit)
Recovery of Online Redo Log: Thread 1 Group 11 Seq 331 Reading mem 0
Mem# 0: /opt/flash_recovery_area/GOLD/onlinelog/o1_mf_11_77s5s3yt_.log
Thu Oct 20 16:03:59 2011
alter database enable block change tracking using file '/opt/oracle/change_tracking_file.ctf'
Block change tracking file is current.
Starting background process CTWR
Thu Oct 20 16:04:00 2011
CTWR started with pid=35, OS id=8032
Block change tracking service is active.
Completed: alter database enable block change tracking using file '/opt/oracle/change_tracking_file.ctf'