While MOM/SCOM monitors most events of your OCS system if you are using the OCS Management Pack, there are several events that you need to monitor manually if you not so lucky to have MOM/SCOM
OCS heavy use of certificates also means that when thay expire, your UC solution stops working. Therefor it is recomended to monitor Certificate related events. Heres an example of an early event:
Event Type: Warning
Event Source: OCS Protocol StackEvent
Event ID: 14398
Description:The default outgoing certificate configured for secure transport will expire soon.
Outgoing Certificate for (Default) edge will expire on XXXX Local Time. The certificate serial number is attached for reference.
Also monitor events 14398 and 14342 – A certificate will expire soon, and 14399, 14341, and 14393 – A certificate has expired.
I hope it helps