How to configure Unique Overlay in cn=config

Hello everyone,

I'm trying to configure the uniqueness overlay in Debian Squeeze (OpenLDAP 2.4.23) using "cn=config" but I can't figure how to do it and can't find any good doc about it, the FAQ-O-Matic wasn't very helpful this time.

I've added a new "olcModuleLoad=unique" attribute in "cn=module{0},cn=config" and it hasn't complained, but how and where do I set "olcUniqueURI" ? in "olcDatabase={1}hdb,cn=config" ? This attribute does not seem to be present in my OpenLDAP installation, do I have to add any new schema?

Any reference to documentation explaining how to configure "unique" overlay within "cn=config" would be much appreciated. A dump of a "cn=config" branch correctly configured would be fantastic.

Thanks.