Our server hangs from time to time. It runs well for weeks then the cpu utilization increases slowly. If we are lucky we recognize it at time. After a reboot everything is OK again for a certain period of time.
If we don't notice it at time it's getting slower and slower and hangs or even shows a grey screen only. There is no possibility of accessing it anymore neither direct or by remote tools.
Can please anybody suggest how to work on?
Abend Log doesn't show anything also the other logs don't lighten up the situation for me.

Thanks in advance