We experience hundreds of sessions going in suspended state on rare occasions.
When it happens there is no increase in terms of resource usage - CPU or memory. Rather there is a small amount of decrease 5-10% on CPU.
There is no single error on the SQL log.
I know this will be a blind question but what might be causing this? Any suggestions to check in SQL Server like plan cache etc..?

  • What are they waiting on? Sounds like a blocking chain. – Martin Smith Oct 21 '16 at 14:03
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    What does sp_WhoIsActive say? Or, at least, what is Activity Monitor telling about wait types? – Marcin S. Oct 21 '16 at 14:08
  • There should be a spid that must have been blocking another one and so on . Find that parent blocking spid and check what is it waiting for. That should give you an idea – karun_r Oct 21 '16 at 14:09
  • Foremost wait type is PageLatch_Up: 400 minutes of waiting over 1 minute! Second wait type is PageLatch_Sh: 166 minutes of waiting over 1 minute – Stackoverflowuser Oct 21 '16 at 14:43
  • My monitoring tool confirms there were no blocking sessions. – Stackoverflowuser Oct 21 '16 at 14:44

It was tempdb contention. Adding more tempdb data files and enabling trace flag 1118 solved the issue.

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