Managing Backup Windows and Performance

Database : 10.2.0.1.0
OS : Linux

A backup window is a period of time during which a backup activity must complete

The BACKUP command supports a DURATION argument which lets you specify how long a given backup job is allowed to run.

Example :

BACKUP DURATION 1:00 TABLESPACE users;


Note : RMAN backs up the specified data at the maximum possible speed. If the backup is not complete in one hours, the backup is interrupted. Any completed backupsets are retained and can be used in restore operations, even if the entire backup is not complete. Any incomplete backupsets are discarded.

By default, when a BACKUP... DURATION command runs out of time before the backup completes, RMAN reports an error. (The effect of this is that if the command is running in a RUN block, the RUN block terminates.)

You can control this behavior by adding the PARTIAL option to the BACKUP... DURATION command.

BACKUP DURATION 1:00 PARTIAL TABLESPACE users FILESPERSET 1;


When PARTIAL is used, no error is reported when a backup command is interrupted due to the end of the backup window. Instead, a message showing which files could not be backed will be displayed. If the BACKUP command is part of a RUN block, then the remaining commands in the RUN block will continue to execute.

When using DURATION the least recently backed up files are backed up first.

Managing Backup Performance with MINIMIZE TIME and MINIMIZE LOAD

When using DURATION you can run the backup with the maximum possible performance, or run as slowly as possible while still finishing within the allotted time, to minimize the performance impact of backup tasks. To maximize performance, use the MINIMIZE TIME option with DURATION.


BACKUP DURATION 1:00 PARTIAL MINIMIZE TIME DATABASE FILESPERSET 1;


To extend the backup to use the full time available, use the MINIMIZE LOAD option.

BACKUP DURATION 4:00 PARTIAL MINIMIZE LOAD DATABASE FILESPERSET 1;



RMAN monitors the progress of the running backup, and periodically estimates how long the backup will take to complete at its present rate. If RMAN estimates that the backup will finish before the end of the backup window, it slows down the rate of backup so that the full available duration will be used. This reduces the overhead on the database associated with the backup.