This causes high utilization on 1 server every day and very slow logins. How can I fix this?

Novell Netware, V6.5 Support Pack 9 - Developement Internal Release
Support Pack Revision 09
(C) Copyright 1983-2008 Novell Inc. All Rights Reserved. Patent Pending.
Server Version 5.70.08 June 15, 2010
Novell eDirectory Version 8.8 SP5 SMP
NDS Version 20505.07 September 22, 2010