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Example: Piecemeal Restore of Database (Full Recovery Model)

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Applies to: SQL Server

A piecemeal restore sequence restores and recovers a database in stages at the filegroup level, beginning with the primary and all read-write, secondary filegroups.

In this example, database adb is restored to a new computer after a disaster. The database is using the full recovery model; therefore, before the restore starts, a tail-log backup must be taken of the database. Before the disaster, all the filegroups are online. Filegroup B is read-only. All of the secondary filegroups must be restored, but they are restored in order of importance: A (highest), C, and lastly B. In this example, there are four log backups, including the tail-log backup.

Tail-Log Backup

Before restoring the database, the database administrator must back up the tail of the log. Because the database is damaged, creating the tail-log backup requires using the NO_TRUNCATE option:

BACKUP LOG adb TO tailLogBackup WITH NORECOVERY, NO_TRUNCATE

The tail-log backup is the last backup that is applied in the following restore sequences.

Restore Sequences

Note

The syntax for an online restore sequence is the same as for an offline restore sequence.

  1. Partial restore of the primary and secondary filegroup A.

    RESTORE DATABASE adb FILEGROUP='Primary' FROM backup1   
   WITH PARTIAL, NORECOVERY  
RESTORE DATABASE adb FILEGROUP='A' FROM backup2   
   WITH NORECOVERY  
RESTORE LOG adb FROM log_backup3 WITH NORECOVERY  
RESTORE LOG adb FROM log_backup4 WITH NORECOVERY  
RESTORE LOG adb FROM log_backup5 WITH NORECOVERY  
RESTORE LOG adb FROM tailLogBackup WITH RECOVERY

  2. Online restore of filegroup C.

    At this point, the primary filegroup and secondary filegroup A are online. All the files in filegroups B and C are recovery pending, and the filegroups are offline.

    Messages from the last RESTORE LOG statement in step 1 indicate that rollback of transactions that involve filegroup C was deferred, because this filegroup is not available. Regular operations can continue, but locks are held by these transactions and log truncation will not occur until the rollback can complete.

    In the second restore sequence, the database administrator restores filegroup C:

    RESTORE DATABASE adb FILEGROUP='C' FROM backup2a WITH NORECOVERY  
RESTORE LOG adb FROM log_backup3 WITH NORECOVERY  
RESTORE LOG adb FROM log_backup4 WITH NORECOVERY  
RESTORE LOG adb FROM log_backup5 WITH NORECOVERY  
RESTORE LOG adb FROM tailLogBackup WITH RECOVERY

    At this point the primary and filegroups A and C are online. Files in filegroup B remain recovery pending, with the filegroup offline. Deferred transactions have been resolved, and log truncation occurs.

  3. Online restore of filegroup B.

In the third restore sequence, the database administrator restores filegroup B. The backup of filegroup B was taken after the filegroup became read-only; therefore, it does not have to be rolled forward during recovery.

RESTORE DATABASE adb FILEGROUP='B' FROM backup2b WITH RECOVERY

All filegroups are now online.

Additional Examples

See Also

BACKUP (Transact-SQL)
Online Restore (SQL Server)
Apply Transaction Log Backups (SQL Server)
RESTORE (Transact-SQL)
Piecemeal Restores (SQL Server)