DBA Tips Archive for Oracle



by Jeff Hunter, Sr. Database Administrator

When setting up the target database for use with RMAN, you need to consider how long you will want to keep backup records to be stored in the control file. This would include records of full database backups, specific datafile, control file, parameter file, and archive log backups. The DBA can use the parameter, CONTROL_FILE_RECORD_KEEP_TIME, to define the number of days (the default being 7) Oracle will keep. For example, if you set this parameter to 5, then Oracle will guarantee to maintain RMAN backup and recovery records for a period of five days.

This parameter has several operational database impacts. For example, it directly impacts the size of the database control file, because as RMAN backups occur, records relating to those backups are stored in the control file. As records are being saved to the control file, it is possible that the control file may run out of space. If this happens, then Oracle will expand the control file to accommodate the storage of the required number of backup records. If you were to set this value to zero, then Oracle will disallow any control file growth which can result in uncertain RMAN backup history retention period.

It is suggested that the DBA set the CONTROL_FILE_RECORD_KEEP_TIME parameter to a value no less than the database backup retention period. Otherwise, the DBA risks having database backups available on the backup media without related backup records available in the control file. This can cause serious complications if you need to recover these older database backups for some reason.

NOTE: From Metalink: Doc ID: 47322.1

This parameter applies only to records in the control file that are circularly reusable (such as archive log records and various backup records). It does not apply to records such as datafile, tablespace, and redo thread records, which are never reused unless the corresponding object is dropped from the tablespace.

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