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Database FlashSnap offers three options for creating database snapshots. The option you choose is specified in the snapplan.
With this option, the tablespaces are put into online backup mode before the snapshot is created. This type of snapshot is also a valid database backup. Select this option if you are performing a point-in-time recovery from logical errors.
With this option, the database can be up and running, and the tablespaces do not need to be put into online backup mode before the snapshot is created. However, all the file systems used by the database (including those containing the online redo logs and control files) are temporarily frozen and the cache is flushed before the snapshot is created. By freezing the file systems, the snapshot will be a consistent point-in-time image of the database from which a database clone can be created.
An instant snapshot can be used to guard against data corruption or for off-host decision-support queries. However, it is not a valid database backup and cannot be used to perform a point-in-time recovery or off-host backup since tablespaces are not put into online backup mode before the snapshot is created. The instant option is much faster than the online option.
The offline option can be used to clone or back up a database. With this option, the database must be shut down when the snapshot is created and online redo logs are required. This type of snapshot is a valid database backup.
In this release of Veritas Storage Foundation for Oracle RAC, Database FlashSnap supports third mirror break-off snapshots only. Third mirror break-off snapshots are fully synchronized, full-sized snapshots.
See the Veritas Volume Manager Administrator's Guide for more information.