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Connor McDonald

Thanks for the question, Harinderjit.

Asked: April 22, 2017 - 6:35 am UTC

Last updated: April 24, 2017 - 1:49 am UTC

Version: 11.2.0.4

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You Asked

Hi Tom,

In AWRs, under the section "IOStat by Function summary", we find a statistic called "Buffer Cache Reads Avg Time"

According to my understanding it is the avg time taken to do a "Buffer Get", Am I right?

I can see in my Production Database this value is ~10ms which I think is huge as we are reading from memory not a disk (in comparison, disk response time is better than this value ie 7ms ).

What is the optimal value for this stat?

Regards,
Harinderjit

and Connor said...

No, these are reads *into* the buffer cache (from disk).

But 10ms isnt great even from disk :-)

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Comments

A reader, April 22, 2017 - 2:15 pm UTC

Thank you Connor.

Stat for Buffer get

A reader, April 22, 2017 - 2:22 pm UTC

Hi Connor,

Thanks for calrification.

Is there a statistic to measure avg time for each "Buffer get" in AWR ?

Regards,
Harinderjit
Connor McDonald
April 24, 2017 - 1:49 am UTC

Not to my knowledge.

There are some undocumented methods to do so...so I'm not really at liberty to reveal them, but if you google: "trace logical io", then ... well... :-)

Harinderjit, April 24, 2017 - 2:50 am UTC

That helps.

Thanks Connor.


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