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So we had some slow performance with timeouts this morning. When looking for the cause, our blocking query (uses DMVs) showed up as the blocking query. I think this was just a fluke but the job we use to get the blocking details was running 4 to 5 times slower than normal. I believe this is just a side effect of whatever was causing the timeouts.

So my question is whether querying the DMVs could actually cause blocking for queries on other tables? Doesn't seem logical.

Using:

dm_exec_sql_text
dm_os_waiting_tasks
dm_tran_locks
dm_exec_sessions
dm_exec_requests

marked as duplicate by Jon Seigel, Paul White says GoFundMonica, Mark Storey-Smith, Marian, Kin Shah May 1 '14 at 12:10

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    I've seen several people report that some of these DMVs can cause blocking. They will often suggest you use READ UNCOMMITTED (NOLOCK) against them - which is a much less egregious thing than doing that against real data. – Aaron Bertrand Apr 30 '14 at 16:48