Global Catalog (GC)
Definition - What does Global Catalog (GC) mean?
A global catalog is a distributed data storage that is stored in domain controllers (also known as global catalog servers) and is used for faster searching. It provides a searchable catalog of all objects in every domain in a multi-domain Active Directory Domain Services (AD DS). A global catalog provides a partial representation of the objects and is distributed using multi-master replication.
Techopedia explains Global Catalog (GC)
A global catalog is a multi-domain catalog that allows for faster searching of objects without the need for a domain name. It helps in locating an object from any domain by using its partial, read-only replica stored in a domain controller. As it uses only partial information and a set of attributes that are most commonly used for searching, the objects from all domains, even in a large forest, can be represented by a single database of a global catalog server.
A global catalog is created and maintained by the AD DS replication system. The predefined attributes that are copied into a global catalog are known as the Partial Attribute Set (PAS). Users are allowed to add or delete the attributes stored in a global catalog and thus change the database schema.
Some of the common global catalog usage scenarios are as follows:
- Forest-wide searches
- User logon
- Universal group membership caching
- Exchange address book lookups