Block Change Tracking(BCT):
It improves the performance of incremental backups by recording changed blocks in the block change tracking file.It is used when an incremental backup is done,instead of scanning all the data blocks to identify which blocks have changed.RMAN uses this file to identify the changed blocks that need to be backed up.By enabling this feature it causes slowness in performance.
After enabling BCT a new process Change Tracking Writer(CTWR) starts.
1)Enable the BCT by specifying the location of block change tracking file.
2)View the BCT filename and status in the v$block_change_tracking view.
3)See the sid,program/process and status in the v$session view,this is used to check whether the CTWR process has started or not.
4)Verify CTWR process in v$sgastat view.
5)Then,disable the block change tracking feature.
