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General question on dbms_stats [message #616274] Sat, 14 June 2014 08:00 Go to next message
kiranrathodkr916
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General question on dbms_stats and auto sample size?

what is the impact of having IOTs with overflows and you switch to auto_sample_size and enable approximate NDV .

How does it impact?
Re: General question on dbms_stats [message #616276 is a reply to message #616274] Sat, 14 June 2014 09:45 Go to previous messageGo to next message
Michel Cadot
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if something changes in the statistics, as the optimizer uses the statistics, it is obvious there will be some changes in the execution plans.
How? It depends on your objects and data and how you query/use them.

[Updated on: Sat, 14 June 2014 09:45]

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Re: General question on dbms_stats [message #616277 is a reply to message #616274] Sat, 14 June 2014 10:43 Go to previous message
Lalit Kumar B
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kiranrathodkr916 wrote on Sat, 14 June 2014 18:30

what is the impact of having IOTs with overflows and you switch to auto_sample_size and enable approximate NDV .


Yes, there have had been several discussions on this and conclusion was :

A quote from J.Lewis Quote:

if you've got IOTs with overflows and you switch to auto_sample_size and enable approximate NDV then the time taken to gather stats on those IOTs may (depending to a large extent on the data clustering) take much longer than it used to.


For more information look at this link http://jonathanlewis.wordpress.com/2014/03/02/auto-sample-size/
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