Retention policy and Recovery Window

Retention policy:

Assume the following retention policy illustrated in figure below. The retention policy has the following aspects:

·         The recovery window is 7 days.

·         Database backups are scheduled every two weeks on these days:

o        January 1

o        January 15

o        January 29

o        February 12

·         The database runs in ARCHIVELOG mode, and archived logs are saved on disk only as long as needed for the retention policy.

Part 1

As illustrated in Figure , the current time is January 23 and the point of recoverability is January 16. Hence, the January 14 backup is needed for recovery, and so are the archived logs from log sequence 500 through 850. The logs before 500 and the January 1 backup are obsolete because they are not needed for recovery to a point within the window.

Assume the same scenario a week later, as depicted in 

 Recovery Window, Part 2

In this scenario, the current time is January 30 and the point of recoverability is January 23. Note how the January 14 backup is not obsolete even though a more recent backup (January 28) exists in the recovery window. This situation occurs because restoring the January 28 backup does not enable you to recover to the earliest time in the window, January 23. To ensure recoverability to any point within the window, you must save the January 14 backup as well as all archived redo logs from log sequence 500 to 1150.

CONTROL_FILE_RECORD_KEEP_TIME = retention period + level 0 backup interval + 1

for e.g.

 Level 0 backup once a week with retention policy of a recovery windows of 14 days then in this
case the CONTROL_FILE_RECORD_KEEP_TIME should be 14+7+1=22

Regards,

Navaneeth