Microsoft KB Archive/316796

= XADM: A Patch File Is Not Created During Backup =

Article ID: 316796

Article Last Modified on 2/28/2007

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APPLIES TO


 * Microsoft Exchange 2000 Server Standard Edition

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This article was previously published under Q316796





SUMMARY
In Exchange 2000 Server Service Pack 2 (SP2), the backup and restoration process is changed so that Exchange 2000 no longer creates a patch file (.pat) during the backup. In earlier versions of Exchange 2000, you can see the patch file during an online backup, and the patch file is restored when you restore an online backup.



MORE INFORMATION
Online backups interact with the Extensible Storage Engine (ESE) to back up an ESE database without stopping the associated service. In versions earlier than Exchange 2000 SP2, if certain types of transactions occur while the database is being backed up, that data might be added to a patch file. When the ESE performs hard recovery (the process of making a database from an online backup ready to start), that data is read from the patch file (instead of the transaction log files) and applied to the database.

If the patch file is not found or is damaged, hard recovery cannot run and the database must be restored again. In certain circumstances, an administrator might inadvertently trigger soft recovery, which causes recovery to run without applying data from the patch file to the database. If this issue occurs, the database is corrupted and must be restored again. An additional complication is that the administrator may not realize that this issue occurred; the database may appear to be intact and may start without error, but may exhibit symptoms of the corruption at a later time.

To avoid this issue and simplify the backup and restoration process, the need for the patch file is removed in Exchange 2000 SP2.

NOTE: Exchange 2000 SP2 updates the internal version of the database. You cannot restore a database from an earlier version of Exchange 2000 to an Exchange 2000 SP2 computer. If Exchange 2000 SP2 allowed such a restoration to continue, the database would likely be corrupted because backups from earlier versions of Exchange include a patch file. Any data in the restored patch file would not be incorporated with the database during recovery. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

316794 XADM: Exchange 2000 SP2 Does Not Allow You to Restore Exchange 2000 or Exchange 2000 SP1

Additional query words: jet JET_errOutOfBuffers

Keywords: kbinfo KB316796

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