Oracle 19c-Rman Performance of Block change Tracking (BCT)

Description:-

In this article we are going to see use of Oracle Block Change Tracking concept in 19c database.

19c-Block Change Tracking(BCT)

• Oracle 10g introduced the Block change tracking (BCT) feature which is used to Speed up Rman Incremental Backup.
• After Enabling this feature records the modified since last backup and stores the log of it in a block change tracking file using the CTWR (Change Tracking Writer) process.
• Records the modified since last backup and stores the log of it in a block change tracking file.
• Block change tracking feature is not reading the entire database blocks it just directly reads only changed blocks results in block change tracking file.
• During backups Rman uses the log file to identify the specific blocks that must be backed up.
• It improves the Rman performance as it is not scan whole datafiles instead of read the changed blocks and take backups .

Enable Block Change Tracking.

SQL> alter database enable block change tracking using file '/u01/CLONE/datafile/blockfile.log'
 
Database altered.

Select filename,status from V$block_change_tracking;

SQL> Select filename,status from V$block_change_tracking;

FILENAME                                    STATUS
----------                                 -----------
/u01/CLONE/datafile/blockfile.log           ENABLED

Ctwr (change tracking writer process started)

SQL> select * from v$sgastat where name like '%CTWR%';

POOL	       NAME			       BYTES	 CON_ID
-------------- -------------------------- ---------- ----------
large pool     CTWR dba buffer		     1961984	      0

SQL> select sid,program,status from v$session where program like '%CTWR%';

       SID PROGRAM					    STATUS
---------- ------------------------------------------------ --------
	68 oracle@ram.doyen.com (CTWR)			    ACTIVE

Disable block change Tracking

SQL> alter database disable block change tracking;

Database altered.

SQL> select sid,program,status from v$session where program like '%CTWR%';

no rows selected

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