Consider the following scenario:

• On a computer that is running Microsoft SQL Server 2005 or Microsoft SQL Server 2008, you have a large query that contains lots of conjunctions and disjunctions. For example, the query has eight thousand disjunctions that have three conjunctions each.
• These conjunctions and disjunctions are in some specific order.
• You have configured database mirroring.
• A non-yielding issue occurs when SQL Server executes the query.

In this scenario, a database mirroring failover may occur unexpectedly.

Note A non-yielding issue occurs when an instance of SQL Server processes a single query and does not let other queries proceed. If such a query is executed on a principal instance of SQL Server, and if the time that this instance is non-yielding exceeds the time-out period of the database mirroring operation, then a database mirroring failover may occur.

The SQL Server optimizer does not yield when it analyzes the index usage of the query.

SQL Server 2005

The fix for this issue was first released in Cumulative Update 8 for SQL Server 2005 Service Pack 3. For more information about this cumulative update package, click the following article number to view the article in the Microsoft Knowledge Base:Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2005 fix release. We recommend that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base: - Microsoft SQL Server 2005 hotfixes are created for specific SQL Server service packs. You must apply a SQL Server 2005 Service Pack 3 hotfix to an installation of SQL Server 2005 Service Pack 3. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.

SQL Server 2008

The fix for this issue was first released in Cumulative Update 10. For more information about how to obtain this cumulative update package for SQL Server 2008, click the following article number to view the article in the Microsoft Knowledge Base:Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2008 fix release. We recommend that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

SQL Server 2008 Service Pack 1

The fix for this issue was first released in Cumulative Update 7 for SQL Server 2008 Service Pack 1. For more information about this cumulative update package, click the following article number to view the article in the Microsoft Knowledge Base:Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2008 fix release. We recommend that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft SQL Server 2008 hotfixes are created for specific SQL Server service packs. You must apply a SQL Server 2008 Service Pack 1 hotfix to an installation of SQL Server 2008 Service Pack 1. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.

Hotfix information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

For all supported x86-based versions of SQL Server 2005

For all supported x64-based versions of SQL Server 2005

For all supported IA-64-based versions of SQL Server 2005

For all supported x86-based versions of SQL Server 2008 Service Pack 1 (SP1)

For all supported x64-based versions of SQL Server 2008 SP1

For all supported IA-64-based versions of SQL Server 2008 SP1

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.