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Trace flag 4199


Trace flag 4199

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colin.Leversuch-Roberts
colin.Leversuch-Roberts
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Generally do you run with this on or off?
I've always been slightly worried about setting this trace flag to ON as I don't really have any load like production on any other environment; however I'm thinking running without optimiser fixes may not be the best idea, for the system in question there's a lots of very complex and heavy sql and any performance improvements would be helpful < grin >

The GrumpyOldDBA
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/
andrecesarr
andrecesarr
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Hi!

I work with more than 300 instances of SQL SERVER (all versions) and in all of it, we use this trace flag without problems Smile

Regards,

André CR
TheSQLGuru
TheSQLGuru
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colin.Leversuch-Roberts (3/11/2013)
Generally do you run with this on or off?
I've always been slightly worried about setting this trace flag to ON as I don't really have any load like production on any other environment; however I'm thinking running without optimiser fixes may not be the best idea, for the system in question there's a lots of very complex and heavy sql and any performance improvements would be helpful < grin >


As you note there are quite a few optimizer "fixes" covered by that TF. The issue as always is what if a particular system or even single query gets regressed by one of those fixes?? That could be devastating for a particular application. You either test fully to KNOW you are good or you put it on and hope for the best. There is no middle ground here IMHO. I will say that I am in agreement with you and WANT those fixes enabled if I don't get those ugly regressions.

Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
colin.Leversuch-Roberts
colin.Leversuch-Roberts
SSCarpal Tunnel
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I'm going to progress it through my environments the same as patches. Hopefully if there is an issue my monitoring and/or the testers will pick it up before we get to production.

The GrumpyOldDBA
www.grumpyolddba.co.uk
http://sqlblogcasts.com/blogs/grumpyolddba/
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