What Is Global Catalog?

The purpose of LDAP is to allow network users to search and find the objects in the Active Directory they want to use. For this to happen, the Active Directory domain controllers maintain a "global catalog." The global catalog allows users and applications to find objects in the Active Directory by searching for a particular attribute(s). The global catalog holds a partial "replica" of the objects and their most common attributes. When a user performs a search operation to find a user (or other object), the global catalog is checked to find matches for that request. The global catalog looks for that attribute and returns matches to the user. Data in the global catalog is built and maintained through replication among domain Controller.