Topic Last Modified: 2006-04-27

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine if the Initial Reserve Size KB registry entry is present:


If the Exchange Server Analyzer finds the Initial Reserve Size KB registry value present and configured with a value greater than 0, a non-default configuration message is displayed.

The Initial Reserve Size KB registry value is used to set aside additional memory for heap space. The value specified is in kilobytes. The default value on most Exchange servers is 655360 kilobytes (KB), which equals 640 megabytes (MB). You can reduce this value to increase the amount of available free memory and reduce virtual memory fragmentation. This value should only be set on the advice and direction of Microsoft Product Support Services support professionals. This message is an informational message and no corrective action needs to be taken if this registry value was added on the advice of Microsoft Product Support Services support professionals.

If you believe this entry was incorrectly set, you can remove it and revert to the default configuration.

This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To revert to the default configuration settings

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\System\CurrentControlSet\Services\MSexchangeIS\ParametersSystem

  3. Delete the value called Initial Reserve Size KB.

  4. Close the registry editor, and then restart the Microsoft Exchange Information Store service for the change to take effect.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (

For more information about troubleshooting virtual memory fragmentation, see the Knowledge Base article, "HOW TO: Troubleshoot Virtual Memory Fragmentation in Exchange 2003 and Exchange 2000" (