FIX: Size of a data file that is committed by online page compression is larger than that is committed by offline page compression in SQL Server 2008 or in SQL Server 2008 R2

Microsoft distributes Microsoft SQL Server 2008 Service Pack 1 (SP1) or Microsoft SQL Server 2008 Service Pack 2 (SP2) fixes as one downloadable file. Because the fixes are cumulative, each new update release contains all the hotfixes and all the security updates that were included with the previous SQL Server 2008 SP1 or Microsoft SQL Server 2008 SP2 update release.

When you perform a page compression in Microsoft SQL Server 2008 or in Microsoft SQL Server 2008 R2, the compressed file is larger if you run online page compression than if you run offline page compression.

This issue occurs because some pages are not compressed by an online page-compression operation.

An online page-compression operation requires the Exclusive lock on the pages. However, the Intent Exclusive lock is used to lock the pages. Therefore, pages are not compressed by an online page-compression operation.

Cumulative update information 

SQL Server 2008 R2

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 R2, 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 R2 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 R2 Service Pack 1

The fix for this issue was first released in Cumulative Update 3 for SQL Server 2008 R2 Service Pack 1. For more information about how to obtain 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 R2 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:

Cumulative update package 16 for SQL Server 2008 SP1

The fix for this issue was first released in cumulative update package 16. For more information about how to obtain this cumulative update package for SQL Server 2008 SP1, click the following article number to view the article in the Microsoft Knowledge Base:Note Because the builds are cumulative, each new update release contains all the hotfixes and all the security updates that were included with the previous SQL Server 2008 SP1 update release. We recommend that you consider applying the most recent update release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Cumulative update package 6 for SQL Server 2008 SP2

The fix for this issue was first released in cumulative update package 6. For more information about how to obtain this cumulative update package for SQL Server 2008 SP2, click the following article number to view the article in the Microsoft Knowledge Base:Note Because the builds are cumulative, each new update release contains all the hotfixes and all the security updates that were included with the previous SQL Server 2008 SP2 update release. We recommend that you consider applying the most recent update release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

To work around this issue, add clustered indexes to the corresponding tables that have to be compressed.

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