RMAN -Block change tracking

Hello DBA’S,

In our Production database(10.2.0.4) , currently we are using a backup  stratergy with
a full backup once a month and an incremental backup each week and the archived logs are backed up once a day.
All backups are directly taken in the  tape drives through a network , These tape drives are located in the different server…

In case of any recovery issues we need to transfer the backup sets from the tape to the disk through the network,so we found that there is some increase in the  recovery time .
And we decided to increase the frequency of the incremental backup in order to reduce its size .So we decided to use the Oracle 10g new feature of Block Change Tracking .

Block change tracking causes the changed database blocks to be flagged in a file.As data blocks change, the Change Tracking Writer (CTWR) background process tracks the changed blocks in a private area of memory. When a commit is issued against the data block, the block change tracking information is copied to a shared area in Large Pool called the CTWR buffer. During the checkpoint, the CTWR process writes the information from the CTWR RAM buffer to the change-tracking file.To achive this we need to enable the block change traking in our database:

SQL> conn sys as sysdba;
connected.

SQL> SELECT status FROM v$block_change_tracking;

STATUS
—————————————-
DISABLED

To enable this you need to create a new file for block change traking.

SQL> ALTER DATABASE ENABLE BLOCK CHANGE TRACKING
  2  using file ‘D:\ORACLE\PRODUCT\10.2.0\ORADATA\PRD\change_track_file.dbf’ reuse;

Database altered.

SQL> SELECT status FROM v$block_change_tracking;

STATUS
—————————————-
ENABLED

If a block is changed in the database, the fact is recorded in this  file:D:\ORACLE\PRODUCT\10.2.0\ORADATA\PRD\change_track_file.dbf.
During incremental backup, RMAN checks this file to see which blocks need to be backed up instead of checking all the blocks of a data file.

It dramatically reduces CPU cycles and speeds up incremental backup in the process.
The block change tracking file, if present, is used automatically by the incremental backup; no special RMAN syntax is required. Using a block change tracking file saves enough time and CPU cycles  to take incremental backups every  night instead of taking once a week.

In case if you want to disable it ,you can use the below syntax.

SQL> ALTER DATABASE DISABLE BLOCK CHANGE TRACKING;
 
Database altered.