About backing up SQL databases

Article:HOWTO24056  |  Created: 2010-01-01  |  Updated: 2011-06-15  |  Article URL http://www.symantec.com/docs/HOWTO24056
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About backing up SQL databases

Backup Exec includes three methods for backing up databases: Full, Differential, and for SQL 2005 or later, Full Copy-only. The full method backs up the entire database including all system tables and filegroups. The differential method backs up only the changes made to the database since the last full backup. The copy method works in the same manner as the full method, except that it does not affect future differential or log backups.

A differential backup is smaller and faster than a full backup, so differential backups can be run more often than full backups. Because differential backups allow the restore of a system only to the point that the differential backup was created, you should also create multiple log backups between the differential backups. Using transaction log backups allows you to recover the database to the exact point of failure.

Consider using differential backups when only a relatively small amount of data changes between full backups, or if the same data changes often. Differential backups may also work well in your environment if you are using the simple recovery model and need backups more often, but cannot spare the time to do frequent full backups. If you are using the full or bulk-logged recovery models, you can use differential backups to decrease the time it takes to roll forward log backups when restoring a database.

If you want to run database backups only, instead of a mix of database and log backups, use the simple recovery model for the database so that the transaction log is automatically truncated when a checkpoint occurs in the database. This helps prevent transaction logs from becoming full since with other recovery models the logs are not cleared after a database backup.

With the simple recovery model, copies of the transactions are not stored in the log file, which prevents transaction log backups from being run.

If you do not run transaction log backups, you can recover the database to the point of the last backup, but you cannot restore the database to the point of failure or to a specific point in time.

The master database can only be backed up with the full method; you cannot use the log or differential methods to back up the master database.

Note:

You cannot back up databases to devices that are attached to a computer on which the Remote Media Agent for Linux Servers is installed.

The SQL Agent supports a mirrored SQL database configuration, although Microsoft places limitations on the mirroring of SQL databases.

These limitations include the following:

  • You cannot back up or restore a mirrored SQL database. If you attempt to back up or restore a mirrored database, the backup job or restore job fails.

  • You cannot restore the primary SQL database while it is configured in a mirrored configuration. To restore the primary SQL database, you must stop database mirroring of the primary database.

  • You can back up a primary SQL database and its transaction logs only if the backup job does not leave the database in a non-recovered state.

See Backing up SQL databases.


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Article URL http://www.symantec.com/docs/HOWTO24056


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