Sun ONE Directory Server 5.1 provides the user identification number (UID) Uniqueness plug-in. By default, the plug-in is not activated. To ensure attribute uniqueness for specific attributes, create a new instance of the Attribute Uniqueness plug-in for each attribute. For more information on the Attribute Uniqueness plug-in, refer to the iPlanet Directory Server 5.1 Administrator's Guide at http://docs.sun.com.
The Referential Integrity plug-in is now off by default. To avoid conflict resolution loops, the Referential Integrity plug-in should only be enabled on one master replica in a multimaster replication environment. Before enabling the Referential Integrity plug-in on servers that issue chaining requests, analyze your performance resource, time, and integrity needs. Integrity checks can consume significant memory and CPU resources.