Overview#NDS Sparse Write Replica
Filtered read/write replicas contain a filtered set of objects or object classes along with a filtered set of attributes and values for those objects. The contents are limited to the types of eDirectory objects and properties specific in the host server's replication filter. Users can read and modify the contents of the replica, and eDirectory can access and change selected object information. The selected changes are then automatically propagated to all replicas.
With filtered replicas, you can have only one filter per server. This means that any filter defined for a server applies to all filtered replicas on that server. You can, however, have as many filtered replicas as you have servers to hold them, although more replicas cause more traffic to keep them synchronized.