Global Catalog

What is the Global Catalog?

A Domain run by Active Directory Domain Services can consist of many partitions or naming contexts. The distinguished name (DN) of an object includes enough information to locate a replica of the partition that holds the object.

Many times however, the user or application does not know the DN of the target object or which partition might contain the object. The global catalog (GC) allows users and applications to find objects in an Active Directory domain tree, given one or more attributes of the target object.

I like to think of the Global Catalog as the search index for Active Directory, similar to how you have a search index for email in Outlook.

Modifying the Global Catalog

At times you may wish to remove or add a domain controller from holding a copy of the Global Catalog. Its recommended that at least one server runs the Global Catalog. Below are the steps to add/remove a DC from being included in replicating the Global Catalog.

1. Open Active Directory Sites and Services.
2. Drop-down to Default-First-Site-Name » Server » [domain controller] » NTDS Settings.
3. Right-click NTDS Settings and select Properties.
4. Check or uncheck Global Catalog.