Issues to consider when you use the database mirroring feature in the initial release of SQL Server 2005
After you use trace flag 1400 to start an instance of the initial release of SQL Server 2005, you can set up and evaluate database mirroring. For more information, see the initial release of SQL Server 2005 Books Online.
Note In SQL Server 2005 SP1 and later versions, trace flag 1400 is ignored.
When you prepare to upgrade to the final release of SQL Server 2005
Set the size of the redo queue to the UNLIMITED value before you upgradeIn the final release of SQL Server 2005, the UNLIMITED value is the only size of the redo queue that is supported. Additionally, the SET PARTNER REDO_QUEUE option of the ALTER DATABASE statement is not supported. To avoid later problems with database mirroring, you must reset the size of any nonconforming databases to the UNLIMITED value before you upgrade.
To view the current setting for the redo queue of the databases on an instance of SQL Server, see the mirroring_redo_queue_type column of the sys.database_mirroring catalog view. The only supported value for a mirrored database is the UNLIMITED value. If the value for a database is the MB value, issue the following Transact-SQL statement for that database on the current principal server.
ALTER DATABASE <database_name> SET PARTNER REDO_QUEUE UNLIMITED
Pause or stop database mirroring before you upgrade either partnerDatabase mirroring does not work if one of the partners is running the final release of SQL Server 2005 and the other partner is running a prerelease version of SQL Server 2005. Before you upgrade either partner, pause or stop database mirroring for every database mirroring session. Then, upgrade both partners, and resume database mirroring.
When you set up and evaluate database mirroringThe SET PARTNER REDO_QUEUE option of the ALTER DATABASE statement is not supported. The UNLIMITED value is the only size of the redo queue that is supported.
When you respond to a problem with the log drive on the principal serverNote The problem with the log drive has been resolved in SQL Server 2005 Service Pack 1 and later versions.
If a problem occurs with the log drive on the principal server, the log records that were already sent to the mirror server and that were replayed on the mirror database might never be written to a disk on the principal server. In this case, a log backup that is taken at this point cannot be applied to the mirror database. Therefore, make sure that you keep the database mirroring session running. As long as the database mirroring session is intact, you can repair the problem with the log drive or you can switch the partner roles. You can switch the partner roles either by having database mirroring fail over and resynchronize or by forcing service to the mirror database. If you force service to the mirror database, any new log records that have not yet reached the mirror server are lost.
Important note Keep database mirroring running. If you turn off database mirroring, you must do a full backup and restore of the database to reestablish database mirroring.
Article ID: 907741 - Last Review: 12/09/2015 03:17:57 - Revision: 2.2
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