Topic Last Modified: 2010-01-25

The Microsoft Exchange Server 2010 Management Pack for System Center Operations Manager monitors the Windows Application log on computers running Exchange 2010 and generates this alert when the events specified in the following Details table are logged.

To learn more about this alert, in Operations Manager, do one or more of the following:


Product Name


Product Version

14.0 (Exchange 2010)

Event ID


Event Source

MSExchange ADAccess

Alert Type


Rule Path

Microsoft Exchange Server/Exchange 2010/Common Components/Active Directory Access

Rule Name

The 'PreloadBaseDNs' and 'PreloadFilters' registry keys don't contain the same number of entries.


This Error event indicates that the DSAccess search preload was configured in the Windows registry, but the number of entries in the PreloadBaseDNs registry key does not match the number of entries in the PreloadFilters registry key. If you set appropriate values for the preload registry keys, you can enhance performance of the Exchange server and reduce load on Active Directory.

A BaseDN is a starting point in the Active Directory hierarchy where any given search will start. The PreloadBaseDNs registry key contains multiple BaseDN entries. The PreloadFilters registry key specifies a search filter. The PreloadFilters registry key also contains multiple entries. Each entry in the PreloadBaseDNs registry key must match an entry in the PreloadFilters registry key.

User Action

To resolve this error, make sure that the number of entries in the PreloadBaseDNs registry key equals the number of entries in the PreloadFilters registry key.

For more information, see Microsoft Knowledge Base article 250572, XCON: Preloading and the DSAccess Cache.

For More Information

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.