While working on an assignment of troubleshooting performance issue few month back I have come across a situation where I have to provide good information about the different waittypes and what they do, while researching a good documentation on wait types I have found the most authentic information on PSS Engineer’s blog where Bob Ward has put them nicely. This blog was published in 2009 but its good to keep handy as reference.

Most of the time wait type says us where the bottleneck are, if you wait types like IO_Completion, PAGE IO LATCH, this is indication for disk IO subsystem has some bottleneck. We have to use perfmon counter to verify this and then work around on resolving this issues.

Let me quote some links for the further reading:

http://blogs.msdn.com/b/psssql/archive/2009/11/03/the-sql-server-wait-type-repository.aspx

http://blogs.msdn.com/b/psssql/archive/2009/11/24/doctor-this-sql-server-appears-to-be-sick.aspx

http://support.microsoft.com/kb/822101

http://blogs.msdn.com/b/psssql/archive/2009/07/08/q-a-on-latches-in-the-sql-server-engine.aspx

-- Hemantgiri S. Goswami (http://www.sql-server-citation.com )