Partial online backups

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Instead of a full backup, you can choose to perform a partial backup of the tablespaces in a database. While SnapManager takes a Snapshot copy of volumes for full backups, SnapManager takes a Snapshot copy of each specified tablespace for partial backups.

Because the tablespace level is the lowest level that Oracle allows into backup mode, SnapManager processes backups at the tablespace level, even if you specify a data file in a tablespace.

With a partial backup, each tablespace exists in backup mode for a shorter amount of time compared to a full backup. During an online backup, the database is always available to users; however, the database must perform more work and the host must perform more physical I/O. In addition, because it is taking Snapshot copies of each tablespace specified or each tablespace containing a specified data file instead of the entire volume, SnapManager takes more Snapshot copies.

SnapManager takes Snapshot copies of specific tablespaces or data files. The partial backup algorithm is a loop that SnapManager repeats until it has taken a Snapshot copy of each specified tablespace or data file.

Although you can perform a partial backup, it is recommended that you always perform a full backup of the entire database.

During a partial backup, SnapManager performs these actions:

  1. Places the tablespace containing the data files into backup mode.

  2. Takes a Snapshot copy of all the volumes used by the tablespace.

  3. Takes the tablespace out of backup mode.

  4. Continues this process, until it has taken a Snapshot copy of all the tablespaces or files.

  5. Forces a log switch and then archives the log files.

  6. Generates backup control files.

  7. Takes a Snapshot copy of the log files and the backup control files.