Microsoft Knowledge Base Article 313994 contains the following summary:
This article explains how to create a new global catalog server. This may be necessary if you need additional global catalog servers
(e.g. to support an Exchange 2000 roll out) or if you want to move the global catalog server role to a different domain controller.
There may be occasions when it is necessary to create a new global catalog to replace an existing one, or to add a new global catalog. Microsoft recommends the following method:
|1.||Create a new global catalog on a second domain controller.|
|2.||Wait for the account and the schema information to replicate to the new global catalog. For single domains, this is relatively straightforward. For multiple domain networks, full replication will take additional time, depending on the complexity of the network. The new global catalog will be created by normal Active Directory (AD) replication and depending on the structure of your AD forest, this replication could take considerable time.|
|3.||Remove the global catalog from the original domain controller (optional).|
By default, Windows 2000 will only place a Global catalog on the first Domain Controller in each AD forest.
To create additional global catalog servers, or to move a global catalog from one domain controller to another, you need to perform these actions manually.