FIX: Transactions that are being committed on the principal server may not be copied to the mirror server when a database mirroring failover occurs in SQL Server 2005

This article describes a SQL Server 2005 hotfix package. Specifically, this article describes the following items:

• The issues that are fixed by the hotfix package
• The prerequisites for installing the hotfix package
• Whether you must restart the computer after you install the hotfix package
• Whether the hotfix package is replaced by any other hotfix package
• Whether you must make any registry changes
• The files that are contained in the hotfix package

Consider the following scenario. In SQL Server 2005, you configure database mirroring for a database that is running in high-availability mode. When you use a client application to commit a transaction, data may be lost in the mirrored database when a failover occurs. However, the client application may still receive the SUCCESS status from the principal server.

This issue occurs because the principal server does not receive an acknowledgement that indicates that the log sequence numbers (LSNs) were hardened on the mirror server. The principal server does not receive the acknowledgement when the failover occurs. This issue occurs if the following conditions are true:

• You commit a transaction on the principal server in the client application.
• The principal server waits for the hardened LSNs in the mirrored database. The mirror server starts to apply the hardened log records to the mirrored database from the oldest hardened log records.
• The witness server and the mirror server perform a failover because the principal server does not respond to the witness server and to the mirror server in the partner time-out period.
• The principal server receives the failover request before the principal server receives the acknowledgement that indicates that the LSNs were hardened on the mirror server. The principal server switches its role from the principal server to the mirror server. Therefore, the database mirroring failover occurs.
• The client application may receive the SUCCESS status from the principal server through the database connectivity API. Therefore, the client application determines that the transaction was committed successfully.

In this scenario, the transaction that you committed is not copied to the mirror server when the failover occurs.

Cumulative update information

The fix for this issue was first released in Cumulative Update 4. For more information about how to obtain this cumulative update package for SQL Server 2005 Service Pack 2, 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. Microsoft recommends 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 2 hotfix to an installation of SQL Server 2005 Service Pack 2. 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 available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must have SQL Server 2005 Service Pack 1 installed. For more information about how to obtain SQL Server 2005 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

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.

SQL Server 2005 32-bit version

SQL Server 2005 x64-based version

SQL Server 2005 Itanium architecture version

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

For more information about the naming schema for SQL Server updates, click the following article number to view the article in the Microsoft Knowledge Base: For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: