Some reasons for the difference:
- A single disk read could get more than 1 block
- queries may already find blocks in the cache and
thus not need a disk read
- a query may revisit the same block over and over
without ever going back to disk
The reason we look at both is 'disk_reads' tell us
what is possibly causing stress on the IO subsystem,
'buffer gets' tells us what is causing stress on cpu.
hth
connor
- Erik Williams <ewilliams_at_brownco.com> wrote: >
> I am trying to identify the most harmful statements
> in an application. From
> the Oracle Performance and Tuning Tips and
> Techniques book, I found two
> statements. Both are looking at the statements
> contained in the v$sqlarea.
> The first looks at statements with a high number of
> buffer gets and the
> other looks at the statements with a high number of
> disk reads. Some of the
> statements appear in both lists, but some in only
> one. If all of the disk
> reads are moving blocks into the buffer cache, what
> is the difference
> between the two measures? Can anyone explain the
> difference between the two
> measures?
>
> Thanks.
> Erik
>
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> --
> Author: Erik Williams
> INET: ewilliams_at_brownco.com
>
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Received on Tue Oct 23 2001 - 16:17:01 CDT
