When many legacy presence users are converted to enhanced presence users at the same time, you experience performance issues in Microsoft Office Communications Server 2007 R2. These performance issues may include the following symptoms:
A heavy load occurs on the back-end server that is running Microsoft SQL Server.
Users who are logged on are logged off.
Most end-user scenarios such as instant messaging, presence, conferencing, and audio/video calls are unreliable.
Note Legacy presence users use Microsoft Office Live Communications Server 2003, use Microsoft Office Live Communications Server 2005, or use Office Live Communications Server 2005 Service Pack 1 (SP1). Enhanced presence users use Microsoft Office Communications Server 2007 or use Microsoft Office Communications Server 2007 R2.
This issue is caused by a non-optimal code path in the SQL Server stored procedure that is used for conversion.
To resolve this issue, apply the following update:
977349 Description of the cumulative update package for Office Communications Server 2007 R2 database: January, 2010
To work around this issue, reduce the number of users who are converted from legacy presence users to enhanced presence users at the same time.