Oracle RMAN Pocket Reference

Backups, Backup Sets, and Backup Pieces

When you issue an RMAN backup command, RMAN creates backup sets, which are logical groupings of physical files. The physical files that RMAN creates on your backup media are called backup pieces. When working with RMAN, you need to understand that the following terms have specific meanings:

RMAN backup

A backup of all or part of your database. This results from issuing an RMAN backup command. A backup consists of one or more backup sets.

Backup set

A logical grouping of backup files -- the backup pieces -- that are created when you issue an RMAN backup command. A backup set is RMAN’s name for a collection of files associated with a backup. A backup set is composed of one or more backup pieces.

Backup piece

A physical binary file created by RMAN during a backup. Backup pieces are written to your backup medium, whether to disk or tape. They contain blocks from the target database’s datafiles, archived redo log files, and control files.

When RMAN constructs a backup piece from datafiles, there are a several rules that it follows:

• A datafile cannot span backup sets.

• A datafile can span backup pieces as long as it stays within one backup set.

• Datafiles and control files can coexist in the same backup sets.

• Archived redo log files are never in the same backup set as datafiles or control files.

RMAN is the only tool that can operate on backup pieces. If you need to restore a file from an RMAN backup, you must use RMAN to do it. There’s no way for you ...