Netscape DIRECTORY SERVER 6.1 - ADMINISTRATOR Administrator's Manual page 463

Table 15-33 Details of UID Uniqueness Plug-In (Continued)
Configurable Enter the following arguments:
Arguments
uid
"DN"
"DN"...
if you want to check for uid attribute uniqueness in all listed
subtrees.
However, enter the following arguments:
attribute="uid"
MarkerObjectclass = "ObjectClassName"
and optionally
requiredObjectClass = "ObjectClassName"
if you want to check for uid attribute uniqueness when adding or
updating entries with the requiredObjectClass, starting from the
parent entry containing the ObjectClass as defined by the
MarkerObjectClass attribute.
Dependencies N/A
This plug-in may slow down Directory Server performance.
Performance
Related Information
In a multimaster replication environment, the UID Uniqueness
plug-in will not work at all and should therefore not be enabled.
If you try to add a new entry to a server where the UID Uniqueness
plug-in is enabled and a referral has been created in a subtree, then
the UID Uniqueness plug-in will not work. It will not work because
if it sees any other error apart from noSuchObject (meaning that the
entry does not already exist), which it will do if a referral is created,
then it will return an operations error preventing you from adding
your new entry. To prevent being blocked by such an operations
error, disable the plug-in on the server where you created the
referral. If, however, you still want to run a UID Uniqueness check,
make sure that you only activate the plug-in on the last of the
referred to servers to prevent it from blocking the referral
mechanism.
Further Information Chapter 17, "Using the Attribute Uniqueness Plug-In."
Server Plug-in Functionality Reference
Chapter 15 Administering Directory Server Plug-Ins 463