How can I move the Active Directory (AD) Global Catalog (GC) to another domain controller (DC)?
You don't actually move the GC between servers. Instead, you simply enable the GC on a new server, then disable the current GC. I explained how to configure a new server as a GC in the FAQ "How do I configure a server as a Global Catalog?".
Keep in mind that if you already have one GC in the domain, you won't want to disable that GC until after your new one has received all the existing GC content. You can check this progress by using Event Viewer to view the Directory Services log. Specifically, you'll want to look for event ID 1119, as this figure shows, which tells you that the new server is now advertising itself as a GC server. Before event ID 1119 appears, you should see event ID 1110, which is the new server advising you of a delay (typically 5 minutes) before the new server will start advertising.
In summary, enabling a new GC is a three-step process: 1. Enable the GC on the new server (open the Microsoft Management Console--MMC--Active Directory Sites and Services snap-in, navigate to Sites, select the name of the site that will contain the new GC server, navigate to Servers, select and expand the name of the new GC server, right-click NTDS Settings in the left-hand pane, select Properties, then select the Global Catalog check box).
2. Wait until event ID 1119 appears in the new GC Directory Services event log.
3. Disable the GC on the old server (in the Active Directory Sites and Services snap-in, navigate to Sites, select the name of the site containing the old GC server, select and expand the name of the old GC server, right-click NTDS Settings in the left-hand pane, select Properties, then clear the Global Catalog check box).
If you add or remove GCs and you use Exchange Server, you must reboot the Exchange servers to let them update the DSAccess topology report and begin using the new GCs--otherwise Exchange won't discover the GCs and use them for DSAccess. To create its AD topology view, DSAccess
1. calls the Directory Service (DS) Locator service
2. retrieves a list of all DCs and GCs from the local AD site
3. contacts each server in the list
4. caches as many as 10 active DCs and 10 active GCs
5. reorders the active-GC list so that domain-local GCs are at the top of the list
6. uses the cached DC and GC server list on a simple round-robin basis for global information lookups.
Thank you very much for your kindness
John Savill is an advisory architect for EMC’s Microsoft consulting practice. He’s an MCITP: Enterprise Administrator for Windows Server 2008 and a nine-time MVP. His latest book is The Complete Guide to Windows Server 2008 (Addison-Wesley).Email address: firstname.lastname@example.org