Re: cache buffers chain latch contention
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 25 Mar 2004 19:44:58 -0000
Notes in-line
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
April 2004 Iceland http://www.index.is/oracleday.php
June 2004 UK - Optimising Oracle Seminar
----- Original Message -----
: From: "Khedr, Waleed" <Waleed.Khedr@xxxxxxx>
: To: <oracle-l@xxxxxxxxxxxxx>
: Sent: Thursday, March 25, 2004 7:08 PM
: Subject: RE: cache buffers chain latch contention
:
:Degree of 8 means 16 workers on 2 CPUs = means magnifying any small
: contention for CPU resources (that will never show up on another system
: if you have more CPU's).
Not necessarily 16 slaves with degree 8.
In fact, the path for this query shows no GROUP BY,
ORDER BY, hash or merge joins, and particularly
no Parallel to Parallel: so it will use only 8 slaves.
Depending on the actual activity, 8 slaves is just
about supportable on 2 CPUs, although that
does depend on a reasonable split of disk and
CPU activity. In this case, degree 4 might be
more sensible.
: Reduce the degree to 2 and see how it works for you.
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