Re: SQL Tuning
From: Stefan Koehler <contact_at_soocs.de>
Date: Mon, 2 May 2016 18:24:11 +0200 (CEST)
Message-ID: <2057900294.1015577.1462206251539.JavaMail.open-xchange_at_app10.ox.hosteurope.de>
Hey Lothar,
physical I/O can cause (high) CPU usage too and only be caught/reflected by getrusage(). Here is an example by Frits of such a behavior: https://fritshoogland.wordpress.com/2013/11/24/when-the-oracle-wait-interface-isnt-enough/
Date: Mon, 2 May 2016 18:24:11 +0200 (CEST)
Message-ID: <2057900294.1015577.1462206251539.JavaMail.open-xchange_at_app10.ox.hosteurope.de>
Hey Lothar,
physical I/O can cause (high) CPU usage too and only be caught/reflected by getrusage(). Here is an example by Frits of such a behavior: https://fritshoogland.wordpress.com/2013/11/24/when-the-oracle-wait-interface-isnt-enough/
In addition be aware that Oracle changed the accounting of direct path wait events (Bug #7448407). The wait event can be "absorbed" but cause CPU usage "in background" which is reflected by return value of getrusage().
Both scenarios could make sense here as Jonathan already pointed out the multiblock I/O possibility.
Best Regards
Stefan Koehler
Freelance Oracle performance consultant and researcher
Homepage: http://www.soocs.de
Twitter: _at_OracleSK
> Lothar Flatz <l.flatz_at_bluewin.ch> hat am 2. Mai 2016 um 17:46 geschrieben:
>
> Hi Jonathan,
>
> what also puzzles me is the CPU time. About the same number of buffer gets, but 10 times more CPU. Can't remember where I have seen that before.
>
> Regards
>
> Lothar
-- http://www.freelists.org/webpage/oracle-lReceived on Mon May 02 2016 - 18:24:11 CEST