Run the CONFIGURE command to enable and disable backup optimization. Backup optimization skips the backup of files in certain circumstances if the identical file or an identical version of the file has already been backed up. Full details on the backup optimization algorithm are provided in “Backup Optimization”.
Note that backup optimization applies only to the following commands:
* BACKUP DATABASE
* BACKUP ARCHIVELOG with ALL or LIKE options
* BACKUP BACKUPSET ALL
You can override optimization at any time by specifying the FORCE option on the BACKUP command. For example, you can run:
BACKUP DATABASE FORCE;
BACKUP ARCHIVELOG ALL FORCE;
By default, backup optimization is configured to OFF. To enable backup optimization, run the following command:
CONFIGURE BACKUP OPTIMIZATION ON;
To disable backup optimization, run the following command:
CONFIGURE BACKUP OPTIMIZATION OFF;
To clear the current backup optimization setting, that is, return backup optimization to its default setting of OFF, run this command:
CONFIGURE BACKUP OPTIMIZATION CLEAR;
如果你对具体的算法感兴趣，可以参考：http://www.youngcow.net/doc/oracle10g/backup.102/b1419/rcmconc1008.htm#i1013400