One of Our database size almost 35T and We need to back up this system twice in a day. Because of the backup duration time(We are using 16 channel and full backup time almost 2,5 hours) That’s why We decided to pass the Cumulative Incremental backup strategy for this system.

We take Level 0(full) backup on weekend and We take Level 1 Cumulative Incremental backup during working days.

We notice that after some days passed, Cumulative Incremental backup size rise up from 1T to 11T. It starts to work like full Level0 backup time duration and backup size.

We have been worked with Oracle Support. The reason for this is that there is a limit on the number of backups that BCT can store, these are 8 by default which means After 8 Incremental backup you need to get Level0 backup or you need to change hidden parameter _bct_bitmaps_per_file dynamically

The limit is set by the “_bct_bitmaps_per_file” parameter. This parameter sets the number of bitmaps to be stored for each datafile, and its default value is 8.  As I mentioned before, In order to avoid this issue one can either run less than 8 incremental backups or can increase the “_bct_bitmaps_per_file” parameter.

Please refer to:
How Many Incremental Backups Can Be Taken When BCT Is Enabled ? [ID 452455.1]