Restore and Recover Operations
Restore and Recover Operations
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As with backup operations, software developers should follow the procedures outlined in the Volume Shadow Copy Service SDK Overview and Reference Guide to restore and recover Microsoft® Exchange Server 2003 database and storage groups. Restore operations available to Exchange Server 2003 are limited to the following types.
|Roll-Forward Recovery||Used when databases in the storage group are lost, but the transaction log files are intact. Restore the individual databases to disk, and then replay the transaction log. If there are multiple transaction log files available from incremental or differential backups, merge the restored log files with the transaction log files still on disk, and then Exchange Server 2003 will use them to recover the database.|
|Point-in-Time Recovery||Used when only transaction log files are lost, or when both transaction log files and database files are lost. If there are multiple transaction log files available from incremental or differential backups, they should all be restored.|
|Full Restore||Used when the whole storage group (databases and log files) must be restored from a full backup.|
The terms restore and recover have distinct meanings in the context of rebuilding storage groups and databases for Exchange Server 2003. Restoring an Exchange Server 2003 storage group involves retrieving data saved at the time of a backup from the backup medium, and then putting that data back onto the disk. Recovering an Exchange Server 2003 database includes not only restoring the data from a backup, but also then applying pending transactions from the available transaction logs.
Restoring an Exchange Server 2003 storage group only restores it up to the point in time when it was backed up; recovering it can bring the database fully up to the status defined by the most recent transaction log. Backup applications for Exchange Server 2003 that use the VSS are responsible only for restoring data back to disk.
When the storage group is mounted, the Exchange store will automatically replay pending transactions by using Exchange Server 2003 soft recovery features. Soft recovery features are initiated when the storage group is mounted after being restored from a backup. When the store determines that the state of the database is not consistent with the end of the log files on disk, it will be begin the soft recovery procedure.
Even when a single database within an Exchange Server 2003 storage group is being restored, then entire storage group must be dismounted. This can either be performed manually by an Exchange Server 2003 administrator in the Exchange System Manager, or programmatically by the requesting backup/restore application using the correct command in the CDO for Exchange Management (CDOEXM) API.
The VSS is only responsible for restoring backed-up data to disk. Exchange Server 2003 restores the databases to a consistent, up-to-date state using existing soft recovery techniques for log playback. The backup/restore application must store the Microsoft® Exchange Server 2003 writer for the Windows Server 2003 Volume Shadow Copy Service metadata with the backed-up data in order to ensure that all information needed to perform a restore operation is available.
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This topic last updated: December 2004
Build: June 2007 (2007.618.1)