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response time [message #343679] Wed, 27 August 2008 16:38 Go to next message
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Registered: June 2008

What might be the different reasons for a same query(querying from one table only) being fired but with response times at different times assuming that the data is same at any point of time.

Other than the table being remained at that point of time in cache.....

Re: response time [message #343682 is a reply to message #343679] Wed, 27 August 2008 16:42 Go to previous messageGo to next message
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Re: response time [message #343710 is a reply to message #343682] Wed, 27 August 2008 21:12 Go to previous messageGo to next message
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Registered: October 2005
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The Oracle Cost Based Optimizer - especially in 10g and later - can come up with two different execution plans for the same query/data.

This can be caused by settings at the session-level (eg. OPTIMIZER_MODE) but it could also occur if dynamic sampling occurred at runtime and different rows were sampled.

It could also be true that you are mistaken - they are not identical. If they are run at different times, the tables may have been re-analysed in the meantime resulting in a different plan.

Ross Leishman
Re: response time [message #343759 is a reply to message #343710] Thu, 28 August 2008 01:24 Go to previous message
Michel Cadot
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In addition, concurrent load is different (on cpu, memory and/or disk), caches content is different (on Oracle and/or OS file system and/or disk array)...

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