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A snapshot storage manager uses albums to efficiently manage snapshots. An album refers to a set of snapshots taken during some period of time. Also, an album provides a place to store additional state required to use snapshots.
The result of a hot copy operation that obtains snapshots from an SSM is one or more albums. Each album contains at least one snapshot and usually contains many snapshots. Each snapshot is a virtual copy of the database, but each album is physically only a small fraction of the total database size. Snapshots are copied and pruned as part of albums.
Each album is identified by a numeric ID. You can query the
SYSTEM.SNAPSHOTS table to obtain the ID of the album that contains a particular snapshot (snapshot ID = transaction ID).
Database options let a database administrator control when an SSM stops adding snapshots to one album and starts adding snapshots to a new album. You want the settings of these options (there are defaults) to be consistent with your policy for removing snapshots. See Specifying the Snapshot Retention Policy and Database Options for When SSMs Open New Albums.
An album alone is not a snapshot or a copy of a database. You invoke a hot copy operation to make a copy of one or more snapshots. You can then use one of those copies to restore to that particular snapshot.