RE: os cache vs. db cache
- From: "Hameed, Amir" <Amir.Hameed@xxxxxxxxx>
- To: <robyn.sands@xxxxxxxxx>, "Allen, Brandon" <Brandon.Allen@xxxxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 9 Jul 2007 18:19:28 -0400
http://blogs.sun.com/glennf/category/Oracle
look at the section "Where do you cache Oracle data?"
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Robyn
Sent: Monday, July 09, 2007 5:34 PM
To: Allen, Brandon; oracle-l
Subject: Re: os cache vs. db cache
Thank you Mark and Brandon,
This is the kind of information I'm looking for; I've read
Steve's stuff but it's been a while and the AIX paper is new to me. I
*think* we need to make some changes in our approach, but right now, I
just want to gather and study as much information on the different
options and approaches as possible.
So, if anyone has additional links, documents or experiences,
I'd appreciate the input.
thank you ... Robyn
On 7/9/07, Allen, Brandon < Brandon.Allen@xxxxxxxxxxx
<mailto:Brandon.Allen@xxxxxxxxxxx> > wrote:
I'd be curious to hear anyone's reasons for preferring
OS cache to DB cache.
It seems pretty clear cut to me that it is better to
allow Oracle to manage its own cache since it has much more knowledge
available internally to help predict which blocks are most likely to be
needed again. I've had good results with CIO (Concurrent, a.k.a
non-buffered, non-inode-locking I/O) on AIX, but I did increase
db_cache_size to make up for the lack of filesystem buffering - in one
case from 600M to 1500M, in another I just used CIO from the beginning
so there was no before/after comparison, but performance has been
excellent with CIO. In the case where I switched from regular, buffered
I/O to CIO and increased db_cache_size from 600M to 1500M, the
performance of a fixed set of batch jobs improved from an average
runtime of 166 minutes to 129 minutes - so a 22% reduction in runtime,
but it's difficult to say how much of that improvement was from
switching to CIO and how much was just due to the increase in
db_cache_size alone.
Here's a great paper specifically on AIX CIO for more
info: http://www-03.ibm.com/servers/aix/whitepapers/db_perf_aix.pdf
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Robyn
Over the years, I've read differing opinions on
balancing the os cache and the database cache.
Privileged/Confidential Information may be contained in
this message or attachments hereto. Please advise immediately if you or
your employer do not consent to Internet email for messages of this
kind. Opinions, conclusions and other information in this message that
do not relate to the official business of this company shall be
understood as neither given nor endorsed by it.
Other related posts:
