To scale tens of millions of objects, a forest is partitioned into domains. Each Active Directory domain controller can be a member of one domain, and domain controllers within the same domain contain the same information. Domain controllers from different domains share the same configuration and schema data, but they do not share the same domain data. In Active Directory, a directory partition is a portion of the directory namespace. Likewise, information that is relevant to the entire forest is replicated separately.
Every domain controller contains the configuration, schema, and domain directory partitions.
Updates to the configuration and schema partitions are replicated to all domain controllers in the forest. Updates to objects in the domain partition are replicated to only domain controllers within the domain. Updates are also replicated to global catalog servers if the update is made to an object attribute that is marked for replication to the global catalog. The domain partition contains a domain container which stores users, computers, groups, and other objects for a specific Windows 2000 domain. Active Directory integrated DNS zone data is also stored in the domain container.