RMAN Restartable Backups or Re-Initiating RMAN Backups

Using the restartable backups feature, RMAN can backup only those files that have not been backup since a specified date. You can use this feature after a failed backup to re-initiate that backup. The unit of restartability is a backup set.

If the backup generates multiple backup sets, then the backups that completed successfully do not have to be rerun. If the entire database is written into one backup set, and if the backup fails halfway through, then entire backup has to be restarted. To take advantage of restartable backups, you can use MAXSETSIZE parameter of the NONE; command, so that backup of database will generate multiple backup set. Note that MAXSETSIZE must be large enough that any file can be accommodated in a single backup piece, because large files cannot span backup piece.

After a failure you can backup all files in the database that were not backed up in the last 24 hours by issuing BACKUP DATABASE NOT BACKED UP SINCE TIME ‘SYSDATE-1’; command. If the SINCE TIME is later than the completion time, then RMAN backs up the file. If you use “BACKUP DATABASE NOT BACKED UP” without the SINCE TIME parameter, then RMAN only backs up files that have never been backed up.

When determining whether a file has been backed up, RMAN compares the SINCE TIME date with the completion time of the most recent backup of the file.