About the Oracle Suggested Backup Strategy

The Oracle suggested strategy is based on creating an image copy of your database. The database rolls forward this copy by using incrementally updated backups. Oracle Enterprise Manager schedules RMAN backup jobs during the overnight hours.

For each data file, the strategy calls for backups as follows:

• At the beginning of day 1 of the strategy (the time the first scheduled job actually runs), RMAN creates an incremental level 0 data file copy. It contains the data file contents at the beginning of day 1.

  If a recovery is required, then the archived redo log files from day 1 can be used to recover to any point during day 1.

• At the beginning of day 2, RMAN creates a differential incremental level 1 backup that contains the blocks changed during day 1.

  If a recovery is required, then RMAN can apply this incremental level 1 to roll forward the level 0 backup to the beginning of day 2. RMAN can use archived redo log files to recover to any point during day 2.

• At the beginning of each day n for day 3 and onward, RMAN applies the level 1 backup from the beginning of day n-1 to the level 0 backup. This action brings the data file copy to its state at the beginning of day n-1. Then, RMAN creates a new level 1 backup that contains the blocks changed during day n-1.

  If a recovery is required, then RMAN can apply this incremental level 1 backup to the data file rolled forward on day n-1 to the beginning of day n. RMAN can use archived redo log files to recover the database to any point during day n.

In the Oracle suggested backup strategy, data file copies have the tag ORA$OEM_LEVEL_0. The differential level 1 incremental backups in this strategy share the same tag. You can safely implement other backup strategies without interfering with the Oracle suggested backup strategy.

Oracle suggested backup strategies also use tape backups in addition to disk backups, but these are beyond the scope of this section.