The physical file format used to store RMAN backup sets
backup set
A backup of one or more datafiles, control files, SPFILEs and archived redo log files. Each backup set consists of one or more binary files called backup pieces. Backup pieces are written in a proprietary format that can only be created or restored by RMAN.
Backup sets are produced by the RMAN BACKUP command. A backup set usually consists of only one backup piece. RMAN divides the contents of a backup set among multiple backup pieces only if you limit the backup piece size using the MAXPIECESIZE option of the ALLOCATE CHANNEL.
Backup Sets and Backup Pieces
RMAN can store backup data in a logical structure called a backup set, which is the smallest unit of an RMAN backup. A backup set contains the data from one or more datafiles, archived redo logs, control files, or server parameter file. Backup sets, which are only created and accessed through RMAN, are the only form in which RMAN can write backups to media managers such as tape drives and tape libraries.
A backup set contains one or more binary files in an RMAN-specific format. Each of these files is known as a backup piece. A backup set can contain multiple datafiles. For example, you can back up 10 datafiles into a single backup set consisting of a single backup piece. In this case, RMAN creates one backup piece as output. The backup set contains only this backup piece.
If you specify the
SECTION SIZE parameter on the BACKUP command, then RMAN produces a multisection backup. This is a backup of a single large file, produced by multiple channels in parallel, each of which produces one backup piece. Each backup piece contains one file section of the file being backed up.
For non-multisection backups, RMAN only records backup sets in the repository that complete successfully. There is no such thing as a partial backup set. This differs from an unsuccessful multisection backup, where it is possible for RMAN metadata to contain a record for a partial backup set. In the latter case, you must use the
DELETE command to delete the partial backup set.
