Make certain that you have not mistaken an active or passive hang for a performance drop. If you are experiencing a performance drop, it could be for one of the following reasons:
Other processes are affecting CPU or disk access
Network problems
High input/ouput rate
Memory swapping
Unindexed searches, such as when an index is missing or when a “!” filter is used
Complex searches, such as searches on static groups, class of service, and roles
Complex updates, such as to static groups, class of service, and roles
Sub-optimum hardware
Sub-optimum system settings, such as fds or keepalive
Directory Server tuned incorrectly