Levels for incremental backups in RMAN

The first backup you should take is an incremental level 0 backup. The level 0 backup is the same as a full backup. You need a full backup as your base backup from which incremental changes are determined. A full RMAN backup (backup full database) cannot be used. RMAN will only use a level 0 backup as a base for other incrementals.

Once you have a level 0 backup, you can take an incremental backup. The incremental level can be any integer from 0 to 4. Most Oracle DBAs only use 0 to 2. If you take a level 2 incremental backup, it will back up any changes since the most recent level 2, 1 or 0 backup. A level 1 incremental backup will back up only those changes since the most recent level 1 or 0 backup.

The way that most Oracle DBAs use RMAN for incremental backups follows this guideline: take a level 2 incremental backup daily and a level 1 incremental backup weekly. The daily incremental backup will get all changes in the last day. The incremental level 1 backup will get all changes for the last week. Normally, an incremental level 0 is taken once a month. You may change the time periods to suit your specific needs.

Life gets better in Oracle 10g with the Incrementally Updated Backup (IUB). With IUB, you take a level 0 backup. A level 1 backup will modify the contents of the level 0 backup with the changes. This way, your level 0 backup is always up to date.