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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.



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