Re: Thank you Oracle Support - cursor_sharing = similiar is deprecated!
- From: Dion Cho <ukja.dion@xxxxxxxxx>
- To: veeeraman@xxxxxxxxx
- Date: Tue, 30 Nov 2010 10:37:27 +0900
I understand similar sharing as :
- Exact sharing for the columns histogram.
- Exact sharing for the columns used as range predicates(between, >=, >, <=,
<, ...)
- Force sharing for the columns none of aboves
Similar sharing with the histogramed-columns and/or ranged-columns would
generate tons of child cursors and reparse would occur for each child
cursor.
================================
Dion Cho - Oracle Performance Storyteller
http://dioncho.wordpress.com (english)
http://ukja.tistory.com (korean)
http://sites.google.com/site/otpack (tpack)
================================
2010/11/30 Ram Raman <veeeraman@xxxxxxxxx>
>
> Thanks for the pointer Carol.
>
> I was reading up on the ML note and I saw this: "This parameter is
> generally overly restrictive in what it actually allows to be shared.
> SIMILAR tells oracle to try and share cursors by replacing all literals with
> binds for legacy applications, but directs that sharing only be performed
> when all the replaced literal values were exactly the same (in the case of
> predicates referencing columns with histograms or using inequality operators
> such as BETWEEN, <, and !=) "
>
> I am confused by what "but directs that sharing only be performed when all
> the replaced literal values were exactly the same" means. I thought SIMILAR
> would make Oracle use the already existing plan without having to reparse in
> case of **different** literal values. Is that the right understanding of
> 'sharing of the cursor' ? If sharing is performed only when replaced literal
> values are the exactly same, wouldnt that make it EXACT and not SIMILAR?
>
> Thanks.
>
> 2010/11/25 <Laimutis.Nedzinskas@xxxxxx>
>
>> nice, one more AI decoration gone.
>>
>>
>>
>> ---------------------------------------------------------------------------------
>>
>> Please consider the environment before printing this e-mail
>>
>>
>>
>> Carol Dacko
>> <dackoc@xxxxxxxxx
>> > To
>> Sent by: Oracle-L Freelists
>> oracle-l-bounce@f <oracle-l@xxxxxxxxxxxxx>
>> reelists.org cc
>>
>> Subject
>> 2010.11.23 18:49 Thank you Oracle Support -
>> cursor_sharing = similiar is
>> deprecated!
>> Please respond to
>> dackoc@xxxxxxxxx
>>
>>
>>
>>
>>
>>
>>
>>
>> Maybe I am the last person to the know but Doc ID: 1169017.1 is the
>> announcement that cursor_sharing = similar is now deprecated in 11g! And
>> the write up is very good. And it is great that they also included in the
>> references the Optimizer Team's blog about it too.
>>
>> So yes, thank you Oracle Support! I really do appreciate this! This will
>> now be one more battle I don't need to fight!
>>
>> Warm regards,
>> Carol Dacko
>> University of Michigan
>>
>>
>>
>> --
>> //www.freelists.org/webpage/oracle-l
>>
>>
>>
>
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