Friday, September 28, 2012

Relation between RMAN retention period and control_file_record_keep_time

SQL> show parameter control_file_record_keep_time

NAME                                 TYPE VALUE
------------------------------------ ---- ------------------------------
control_file_record_keep_time     inte 32

RMAN backup keeps the backup metadata information in the reusable section of the controlfile. Its depends on the parameter mentioned above.

CONTROL_FILE_RECORD_KEEP_TIME specifies the minimum number of days before a reusable record in the control file can be reused. In the event a new record needs to be added to a reusable section and there is not enough space then it will delete the oldest record, which are aged enough.

 
RMAN>CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 30 DAYS;

Backup retention policy on the other hand is the rule to set regarding which backups must be retained (whether on disk or other backup media) to meet the recovery and other requirements.

What happens if the Contro_file_record... parameter is less then the retention policy?

If the CONTROL_FILE_RECORD_KEEP_TIME is less than the retention policy then it may overwrite reusable records prior to obsoleting them in the RMAN metadata. Therfor it is recommended that the CONTROL_FILE_RECORD_KEEP_TIME should set to a higher value than the retention policy.

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