The Unique Attributes feature ensures that the specified
attributes always have unique values within a directory. These attributes
can be specified in two entries only, cn=uniqueattributes,cn=localhost and cn=uniqueattributes,cn=IBMpolicies.
The values for a unique attribute are stored on the server where
the attribute is designated as unique. Search results for unique attributes
are unique for that server's database only. Search results that include
results from referrals might not be unique.
Note: Binary attributes,
operational attributes, configuration attributes, and the objectclass attribute
cannot be designated as unique.