In case it could benefit to anyone, the freeze seems to come when
there're "lots of" "deferring operation: binding" messages
in the slapd logfile. So, we investigated the corresponding client
application and found the way it dealt with LDAP connections
could be a problem with OpenLDAP (it was not with Sun DS 5.2 !).
So, we're now in the process of rewriting the client side LDAP
connections management with a pool, so that at least we don't
see anymore "deferring operation: binding" messages.
By the way, are there well known best practices and pointers to write
clean (from a connection management point of view) LDAP clients,
or at least best practices or "known bad practices" with regards to the
way OpenLDAP deals with connections ?