Exchange Server 2003 and Exchange 2000 Server may experience performance problems when the PDC emulator is used for DSAccess (298879)


The information in this article applies to:

  • Microsoft Exchange 2000 Server
  • Microsoft Exchange Server 2003 Enterprise Edition
  • Microsoft Exchange Server 2003 Standard Edition
This article was previously published under Q298879
Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry

SYMPTOMS

By default, DSAccess chooses the primary domain controller (PDC) emulator operations master role computer to handle requests, which may result in poor performance if other non-Exchange programs are making heavy use of the PDC emulator.

RESOLUTION

To resolve this problem, add the MinUserDC registry value to exclude the PDC emulator from the server list that exchange can use.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To add the MinUserDC registry value:
  1. Start Registry Editor (Regedt32.exe).
  2. Locate and click the following key in the registry:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeDSAccess\Profiles\Default

  3. On the Edit menu, click Add Value, and then add the following registry value:

    Value name: MinUserDC
    Data type: REG_DWORD
    Value data: MinUserDc determines how many total user domain controllers must be available for PDC emulator exclusion to turn on. For example, if there are four domain controllers from the same domain in the same site as the Exchange 2000 server, and one of those domain controllers is the PDC emulator, when this registry key is set to 4, only the three non-PDCs are used as user domain controllers and the configuration domain controller is chosen from the three. If the registry key is set to 5, all four domain controllers are used as user domain controllers, and the configuration domain controller is chosen from the four.

  4. Quit Registry Editor.
Notes
  • You have to apply the registry change that this article describes regardless of which service pack is installed.
  • In Exchange Server 2003 and in Exchange 2000 Server Enterprise Edition, the Profiles key and the Default key are unavailable. You must create these keys in Exchange Server 2003 and in Exchange 2000 Server Enterprise Edition.
  • Make sure to set the value of MinUserDC to 1, regardless of how many domain controllers are in the site. Then, the PDC emulator will be used only if no other domain controller is available.

STATUS

Microsoft has confirmed that this is a problem in Microsoft Exchange 2000 Server.
Modification Type:MinorLast Reviewed:8/31/2006
Keywords:kbbug kbfix KB298879
©2004 Microsoft Corporation. All rights reserved.