January 16, 2019 at 5:52 pm
Feivel - Wednesday, January 16, 2019 12:15 PMJeff Moden - Wednesday, January 16, 2019 8:49 AMpThis sound symptomatic of a problem we had last year. Simple SELECTs getting stuck and going into a KILLED/ROLLBACK that couldn't be killed. It crippled us a couple of times a day.It turned out to be the connections that the apps were using. They all had MARS (Multiple Active Result Sets) enabled even though the default in .NET isn't supposed to do that. We fixed those, the problem went away immediately, and we've not had the problem since. How did it start? I don't know for sure but I suspect it reached some sort of a "tipping point" due to the ever-increasing size of the data an WHAM!
How did you end up resolving the same? I am not sure if my case is relevant to yours but as I mentioned previously do we really know if resource contention would be a reason why these sessions were stuck in that state because I noticed low memory warnings on that server. I am not sure if I can really relate it to anything at this point as I am not sure what answer to provide to the the business folks at my workplace.
Like I said, we changed all the connection strings in the applications. Specifically, we changed the part that enable Mars to specifically disable it.
If you are asking how we figured out that it was MARS causing the problem, my boss got lucky Googling for the symptoms and found post that mentioned it. I don't know what that link was nor what specific words he used for his search.
--Jeff Moden
Change is inevitable... Change for the better is not.
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