An application directory partition is a directory partition that is replicated only to specific domain controllers. A domain controller that participates in the replication of a particular application directory partition hosts a replica of that partition. Only domain controllers running Windows Server 2003 can host a replica of an application directory partition.
Application directory partitions are usually created by the applications that will use them to store and replicate data. TAPI is an example it. For testing and troubleshooting purposes, members of the Enterprise Admins group can manually create or manage application directory partitions using the Ntdsutil command-line tool.
Application directory partitions can contain any type of object, except security principals. The data in it can be replicated to different domain controllers in a forest (for redundancy, availability, or fault tolerance).
