Hello Running Exchange 2007 SP3. We have an Active/Passive SCC Cluster. This morning between 11:00 - 11:20, users called in saying that their Outlook session was freezing and OWA was being unresponsive. Things gradually got worse until users in Outlook said their client could not contact the Exchange server. I ran Test-MAPIConnectivity for the server and it was failing for most stores, or sometimes all, saying that the database did not respond in the alloted time. Looking at Permon, Averaged RPC Latency was sky high during this time - about 400ms. We eventually failed over which resolved the issue. We need to either find out what happened or know what to look for in case this happens again. Does anyone know how we can figure out what caused that spike? Many thanks in advance.

These types of issues (to find root cause) can take time. I would start by using ExMon - http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=11461 and monitor when the issue next occurs. Setup some perform mon monitoring to alert you. As for now, all I can suggest is to look into the event logs. A number of things can cause this, such as Mobile devices/EAS/Outlook pluggins etc. Sukh

Since the issue is resolved by a failover, I am suspecting there might be an issue on database store, or the server performance. Since it is Exchange forum, for performance related issue, I'd suggest you submit a new thread on server forum for permance monitor log analysis at http://social.technet.microsoft.com/Forums/en/category/windowsserver/, your understanding would be appreciated.Fiona