Active Directory Replication

Directory Partition Replicas

A directory partition replica can be a full (master) replica or a partial replica.

A full replica contains all attributes of all directory partition objects and is both readable and writable. Each domain controller stores at least three full, writable directory partition replicas as follows:

The schema partition, which contains all class and attribute definitions for the forest. There is one schema directory partition per forest.
The configuration partition, which contains replication configuration information (and other information) for the forest. There is one configuration directory partition per forest.
The domain partition, which contains all objects that are stored by one domain. There is one domain directory partition for each domain in the forest.

A full replica of a domain's partition is stored on all domain controllers of that domain (and nowhere else); a full replica of a forest's configuration and schema partitions is stored on all domain controllers of that forest (and nowhere else).

A partial replica contains a subset of the attributes of all directory partition objects and is read-only. Partial replicas are stored only on Global Catalog servers. An attribute is contained in a partial replica if and only if the attribute's attributeSchema object has isMemberOfPartialAttributeSet equal to TRUE.

Therefore, on a specific domain controller, a single database stores copies of those objects that are pertinent to only that domain, in addition to copies of the schema and the configuration objects, which apply to all domains in the forest. On domain controllers that are Global Catalog servers, the database also stores partial replicas of directory partition objects from other domains. Partial replicas are stored on Global Catalog servers so that searches of the entire directory can be achieved without requiring referrals from one domain controller to another.

Important

Note the difference between the directory tree (the Windows 2000 forest) and the physical database on a specific domain controller in that forest. The directory includes all of the objects in the forest. The directory database on a specific domain controller in the forest includes replicas of the domain objects for only that domain in addition to the replicas of the configuration and schema objects for the entire forest.

For more information about directory partitions, see "Active Directory Data Storage" in this book. For information about directory searches, see "Name Resolution in Active Directory" in this book. For more information about Global Catalog servers, see "Active Directory Logical Structure" in this book.