XADM: Exchange Considerations for Promoting a Domain Controller to a Global Catalog Server

A known issue with Exchange 2000 and promoting a domain controller to a Global Catalog (GC) server is that you have to restart the server after the promotion by using Active Directory Sites and Services, NTDS Settings.

Exchange 2000 relies heavily on GC servers for full functionality. This article describes how to minimize potential problems when you are promoting a domain controller to a GC in an Exchange 2000 environment. Two significant problems can occur in Exchange 2000 when promoting a domain controller to a GC:

• The Name Service Provider Interface (NSPI) is not automatically enabled.
• The GC can start advertising itself before replication has completed.

Regarding the first point, promoting a domain controller to a GC does not prompt you to reboot, however, the Named Service Provider Interface (NSPI, the API used for Microsoft Outlook Address Book lookups) is not dynamically enabled after domain controller promotion; a reboot is required.

Note: NSPI is only supported on GC servers; Domain controllers do not support NSPI and are never used for Outlook Address Book look-ups. If you promote a computer to a GC without rebooting, SRV records are placed in DNS and the Exchange 2000 System Attendant attempts to use the new server. It detects that NSPI is not enabled and logs the following event in the Application log on the Exchange 2000 server:
Potential replication issues are described in the "More Information" section of this article.

After you have promoted the domain controller, DSAccess places the newly-promoted server into its list of Working GC servers. In this scenario, it is possible that replication may not have completed, so the new server may not have all the information that is expected of a GC server. At a high-level, the resolution to this problem is to promote the domain controller to a GC, prevent it from advertising itself as a GC and to not reboot it until all the partial naming contexts have been replicated. However, to do so, you have to have Windows 2000 Service Pack 2 (SP2) installed.

If you restart the GC before replication is completed, there are some potential issues:

1. DSAccess transfers the new GC list to the Categorizer. In large or complex environments, it is still possible for the Categorizer to reference GCs that have not finished replicating, which results in sporadic non-delivery messages. The effect can be random as the Categorizer may reference a different GC when the user clicks Send Again. Although there is a one-hour delay between receiving a new GC list from DSAccess and attempting to use new servers which appear on the list, this may not be enough time in some environments.
2. If the newly promoted server is rebooted too quickly, the GC will have NSPI enabled and DSProxy will start to use it for address book lookups. However, the replication may still be unfinished, resulting in incomplete address books.

To Promote a Domain Controller to a GC Server in an Exchange 2000 Environment

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

On the domain controller to be promoted, implement the following registry parameter (this step is valid only on Windows 2000 Service Pack 3 or later):

1. Start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NTDS\ Parameters
3. On the Edit menu, click Add Value, and then add the following registry value:
   Value name: Global Catalog Partition Occupancy
   Data type: REG_DWORD
   Radix: Hexadecimal
   Value data: 6
4. Quit Registry Editor.

This registry parameter directs the promotion process to complete the full replication of all naming contexts before advertising itself. By default, the GC promotion runs at partition occupancy level 4, which only requires the naming contexts that are found within the local Active Directory Site to be fully replicated before advertising takes place.

After you implement the registry changes, follow these steps:

1. Stop the Net Logon service on the server to be promoted. This prevents the GC from advertising itself after replication has completed and the 1119 event is reported in the Directory Service log. Event ID 1119 indicates that the promotion to a GC is completed.
2. In the Active Directory Sites and Services, start the promotion process.
3. Monitor the Directory Service log for the 1119 event. This signifies that the GC promotion has fully completed to the partition occupancy level set.
4. Restart the server.

After the server has been rebooted, NSPI is automatically enabled and the server advertises itself in DNS. The DSProxy detects the new server within 15 minutes. However, because you set the partition occupancy level to 6 and you restarted the server, the new GC will be fully operational and will be a valid server for Exchange 2000 and Outlook to use.

For more information about how to promote a domain controller to a Global Catalog server, refer to Windows 2000 Help, or you can refer to the following article in the Microsoft Knowledge Base: