Re: Oracle slowed down

From: Bob Jones <email_at_me.not>
Date: Tue, 25 Apr 2006 23:56:56 GMT
Message-ID: <cHy3g.71986$Jd.22571@newssvr25.news.prodigy.net>

"Brian Peasland" <oracle_dba_at_nospam.peasland.net> wrote in message news:IyAMA3.ApH_at_igsrsparc2.er.usgs.gov...
>> I think they did. If you look at Buffer Cache Size Advice, you'll
>> notice they say "Relative Change in Physical Reads."
>
> Even this is still akin to the BCHR. Increasing or decreasing your buffer
> cache will make changes to the physical reads required to satisfy your
> "normal" workload. But is this really that different than tuning by the
> BCHR? So I decreased by physical reads by 10%. Is that good? It may or may
> not be.

Bingo! BCHR is just one of the indicators, not the only one.

> In some cases, I still have poorly written SQL which needs to be tuned.
> Tuning that SQL can reduce the physical reads as well.

Yes, SQL tuning can reduce physical reads. However, as I have said many times in this thread, SQL and buffer cache tuning are done separately. It wouldn't make much sense to tune one while the other is constanly changing. That why one can only see the relevancy of BCHR, when everything else remains the same.

> Sizing the buffer cache to reduce the physical reads, is the same (in my
> book) as sizing the buffer cache to increase the BCHR.
>
>

Agreed. Received on Tue Apr 25 2006 - 18:56:56 CDT