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RMAN - Backup File Optimization



RMAN - Backup File Optimization Feature

Overall backup times of a database can be reduced when you choose not to back up your read-only or offline tablespaces all the time. It used be quite tedious to track when these tablespaces were last backed up. With Oracle9i, RMAN offers the backup file optimization (BFO) feature.

With BFO, if RMAN is about to back up a file, and the file has already been backed up by the same device type, RMAN will skip the backup of that file. This includes both data files and archived redo logs backed up by RMAN. Oracle determines if the file has changed by comparing the datafile to the header of the backed up datafile. If they match, the file is not backed up.

Before RMAN decides to skip a given datafile, it will determine if the datafile backup that is available meets the established retention policy. If the latest backup violates the retention policy, then RMAN will back up the datafile anyway.

There may be cases when you want to back up all tablespaces. In this case, use the FORCE option of the BACKUP command. Using this option will cause Oracle to back up all datafiles and archived redo logs of the database regarding backup file optimization.

To enable the RMAN optimization feature, use the CONFIGURE command with the BACKUP OPTIMIZATION keywords. The following examples illustrate the use of this command:

RMAN> CONFIGURE BACKUP OPTIMIZATION ON;
RMAN> CONFIGURE BACKUP OPTIMIZATION  OFF;

The first example enables backup optimization. The second command shown in the previous example shows how to disable optimization.


C:\Users\>RMAN

Recovery Manager: Release 10.2.0.1.0 - Production on Fri May 29 20:38:33 2014

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

RMAN> connect target sys@GFFR01

target database Password:
connected to target database: XE (DBID=2761439438)

RMAN> show all;

using target database control file instead of recovery catalog
RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 0 DAYS;
CONFIGURE BACKUP OPTIMIZATION OFF; # default - OPTIMIZATION IS OFF

RMAN> CONFIGURE BACKUP OPTIMIZATION ON;

new RMAN configuration parameters:
CONFIGURE BACKUP OPTIMIZATION ON;
new RMAN configuration parameters are successfully stored

RMAN> show all;

RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 0 DAYS;
CONFIGURE BACKUP OPTIMIZATION ON;

NOTE: In case when you want to back up all table spaces. Use the FORCE option of the BACKUP command. Using this option will cause Oracle to back up all data-files and archived redo logs of the database regarding backup file optimization.

If optimization is ON also. The below command will ignore that parameter and backup all the database files including archive logs as well.;

RMAN> BACKUP FORCE DATABASE;

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