Computer Associates used to recommend excluding particular processes and directories from eTrust anti-virus scanning.  This, I found, was very important with Microsoft SQL Server, as it would cause a significant performance hit.
You would do this via setting the following registry keys, under HKEY_LOCAL_MACHINE\SOFTWARE\ComputerAssociates\eTrustITM\CurrentVersion\Realtime

Reason for exclusion List of processes to be excluded, separated by “|”
Microsoft SQL Server sqlserver.exe  sqlservr.exe
Microsoft Exchange store.exe
and some others …



Reason for exclusion List of directories to be excluded, separated by “|”
Microsoft SQL Server SQL disk devices files directories.
Microsoft Exchange Arctemp
Windows Server %windir%\Tasks
Windows failover cluster Quorum drive
<system root>:\Windows\Cluster
and some others …

Allows you to exclude files based on the file name extension.  Examples for this I have seen include BTR|DB|MDX|NDX|MDW|ASD|TMP|ZMG
I was reminded of these registry keys, when I read Tim McMichael’s TechNet blog post, An interesting issue with file level antivirus…

Updated 26 Nov 2009

Updated 22 Dec 2009 – Added:

Updated 13 Nov 2010 – Added: