The backup method, Database Snapshot (SQL 2005 or later), enables you to do the following:
After selecting the Database Snapshot (SQL 2005 or later) backup method, an option appears called Database snapshots to keep. This option enables you to set the number of database snapshots to be kept on disk for each database. As the threshold is met, older database snapshots are deleted, which are then replaced with new snapshots. Because database snapshots continue to grow as the SQL database is updated, limiting the number of snapshots enables you to minimize both the disk space and SQL Server processing time that is required when the snapshots are updated.
By limiting the number of database snapshots that are kept, you can configure a database protection strategy that minimizes data loss in the event of a host database problem. For example, you can create a strategy that protects the SQL database from inadvertent table deletions. This strategy consists of a Backup Exec database snapshot job that you schedule to run once every hour during a 24 hour period. As part of the strategy, you also configure the job to keep four database snapshots. Because the job is scheduled to run every hour, a new database snapshot is created every hour. Beginning with the fifth hour and going forward, the oldest database snapshot is automatically deleted before a new one is created. Throughout the 24 hour period, there are no more than four database snapshots on disk. If a user deletes a database table, you first determine the time the table was deleted and then run a Backup Exec database snapshot restore job that enables you to revert the host to one of four previous points in time going back four hours. Remember, however, that any changes made to the host between the time a database snapshot is created and the point at which it is reverted, are lost.