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increasing buffer cache....! [message #128457]

Mon, 18 July 2005 12:30

balavignesh
Messages: 180
Registered: March 2005

Senior Member

hai ,

we are using statspack for performance issues.based on that report generated on that , it is found that the buffer hit ratio is below 90% and needs to be increased. it is indicated that buffer size is 78M.but in parameters there is not like that set while shared pool size is there.how to see the buffer cache size and then we have to change it using alter system set and all.plz help out.

regards
bala

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Re: increasing buffer cache....! [message #128460 is a reply to message #128457]

Mon, 18 July 2005 12:56

Mahesh Rajendran
Messages: 10708
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

Buffer Hit Ratio cannot be considered as a Measure for tuning.
You can programmatically Bring the Hitratio to any value you want.
Please see here
http://www.orafaq.com/forum/t/23453/0/

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Re: increasing buffer cache....! [message #128462 is a reply to message #128460]

Mon, 18 July 2005 13:14

balavignesh
Messages: 180
Registered: March 2005

Senior Member

hai mahesh,

the procedure does nt work out , it gives compilation errors.in addition to that , if we increase buffer hit ratio programatically will it increase the performance..?

bala

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Re: increasing buffer cache....! [message #128463 is a reply to message #128462]

Mon, 18 July 2005 13:26

Mahesh Rajendran
Messages: 10708
Registered: March 2002
Location: oracleDocoVille

Senior Member
Account Moderator

>>if we increase buffer hit ratio programatically will it increase the performance..?

That was what Connor McDonald trying to explain.
Buffer hit ratio has nothing to do with performance.
It is some junk number.
Buffer hit ratio based tuning is flawed.

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Re: increasing buffer cache....! [message #128464 is a reply to message #128457]

Mon, 18 July 2005 13:30

smartin
Messages: 1803
Registered: March 2005
Location: Jacksonville, Florida

Senior Member

If you are on 10g, you can set sga_target and forget about tuning the buffer cache, let oracle do it for you. If you are on 9i, I think there is a buffer cache advisory you can run which will give you an idea of the kind of performance results from changing the size. In either case, suggest reading the performance tuning guide and concepts guide sections on memory.

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