clearing SQL cache

Question

clearing SQL cache

vkkrishn

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Points: 17
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April 6, 2010 at 10:58 pm

#220050

Hello,
We have our application running on sql server 2005. Recently we started slowing down of the database and timeouts. Once we clear the SQL cache, it turns normal again. What all can be the causes of this issue we are facing. And what can we do to avoid this. Please help!

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SQLRNNR SSC Guru Points: 281334 More actions · Answer 1

Are you getting any error messages along with the slowdown or are you just experiencing general slowness? Are you seeing application timeouts?

Jason...AKA CirqueDeSQLeil
_______________________________________________
I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
Posting Performance Based Questions - Gail Shaw[/url]
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Dave Ballantyne SSC-Dedicated Points: 33566 More actions · Answer 2

Do you mean the procedure cache (DBCC FREEPROCCACHE) or the buffer cache(DBCC DROPCLEANBUFFERS) ?

Im guessing the former, could potentially be parameter sniffing http://www.sqlpointers.com/2006/11/parameter-sniffing-stored-procedures.html

Clear Sky SQL
My Blog[/url]

Johan Bijnens SSC Guru Points: 135255 More actions · Answer 3

What service pack is your sql2005 on ?

Please post the result of

select @@version

or

Select Serverproperty( 'ProductVersion' ) as ProductVersion

, Serverproperty( 'ProductLevel' ) as ProductLevel

, Serverproperty( 'ResourceLastUpdateDateTime' ) as ResourceLastUpdateDateTime

, Serverproperty( 'ResourceVersion' ) as ResourceVersion

, Serverproperty( 'Edition' ) as Edition

, Serverproperty( 'EditionID' ) as EditionID

What action did you perform to "clear the cache" ?

Johan

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Paul White SSC Guru Points: 150467 More actions · Answer 4

Dave Ballantyne (4/7/2010)
Do you mean the procedure cache (DBCC FREEPROCCACHE) or the buffer cache(DBCC DROPCLEANBUFFERS) ?
Im guessing the former, could potentially be parameter sniffing http://www.sqlpointers.com/2006/11/parameter-sniffing-stored-procedures.html

I like guessing games 🙂

My guess is procedure cache bloat due to ad-hoc queries.

http://blogs.msdn.com/sqlprogrammability/archive/2007/01/23/4-0-useful-queries-on-dmv-s-to-understand-plan-cache-behavior.aspx

DBCC FREESYSTEMCACHE('SQL Plans');

Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi

SQLRNNR SSC Guru Points: 281334 More actions · Answer 5

vkkrishn,

Do you have any of the information / answers for the questions asked?

Jason...AKA CirqueDeSQLeil
_______________________________________________
I have given a name to my pain...MCM SQL Server, MVP
SQL RNNR
Posting Performance Based Questions - Gail Shaw[/url]
Learn Extended Events

Dave Ballantyne SSC-Dedicated Points: 33566 More actions · Answer 6

Paul White NZ (4/7/2010)
My guess is procedure cache bloat due to ad-hoc queries.

Which reminds me , ive still got a half finished blog on forced parametrization hanging around.

Clear Sky SQL
My Blog[/url]

Paul White SSC Guru Points: 150467 More actions · Answer 7

Dave Ballantyne (4/7/2010)
Paul White NZ (4/7/2010)
My guess is procedure cache bloat due to ad-hoc queries.
Which reminds me , ive still got a half finished blog on forced parametrization hanging around.

Well get on with it then!!!

:laugh: 😀 😛

Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi

sam.alexander Ten Centuries Points: 1135 More actions · Answer 8

vkkrishn (4/6/2010)
Hello,
We have our application running on sql server 2005. Recently we started slowing down of the database and timeouts. Once we clear the SQL cache, it turns normal again. What all can be the causes of this issue we are facing. And what can we do to avoid this. Please help!

We ran into this exact situation not long ago, and what I found was SQL created different cached execution plans based on the parameters we were passing into a procedure, and in some cases the cached execution plan, though ran speedy for some parameters ran very inefficiency with other parameters.

Once I found the troublesome procedure my fix was to view the execution plan and create a few indexes so the same, more efficient cached execution plan was created regardless of parameters used, which worked.

The first thing you need to do is determine what process is taking the longest to run. You may be able to monitor your processes and see which ones are taking a long time to run and go from there.

Let me know if you need more details and I can send you some of what we did to find the troublesome procedure then remedy the latency.

Take care --

Sam