I am looking at the Activty Monitor for SQL Server 2005 and we have some processes that are taking up large amounts of the CPU. When I look at what is trying to be run I get:
set transaction isolation level read committed
This code is not coming from any of our applications.
What is causing it?
What should be done?
Look at sys.dm_exec_sessions and sys.dm_exec_connections for the session ids that take up CPU. You'll find the application name, host name and process id of the client.
This is the default transaction isolation level for ADO.NET and most OR/M frameworks. Chances are this is in fact coming for your code, you just don't know it.
I think this is the wrong question to ask anyways - the real question is, why is this rather common TSQL instruction causing your database CPU to spike?
来源：https://stackoverflow.com/questions/1947340/activity-monitor-problems-in-sql-server-2005