RE: Question - any parameter or hint to FORCE Physical Read (bypass buffer cache)
Date: Mon, 22 Apr 2013 15:47:55 -0500
Message-ID: <F05D8DF1FB25F44085DB74CB916678E8879CFE5683_at_NADCWPMSGCMS10.hca.corpad.net>
The amount of IOs per execution I haven't checked. I should/will check that. The plans for the query I'm interested in are really simple and are the same on all 3 nodes.
Chris
From: tanel_at_poderc.com [mailto:tanel_at_poderc.com] On Behalf Of Tanel Poder
Sent: Monday, April 22, 2013 3:45 PM
To: Alex Fatkulin
Cc: Taylor Christopher - Nashville; ORACLE-L
Subject: Re: Question - any parameter or hint to FORCE Physical Read (bypass buffer cache)
_serial_direct_read will use direct path reads for full table scans & fast full index scans only and not the "random" single block reads done for index-based access.
You can make your buffer cache really-really small and run your test then. Or use SLOB or Swingbench (again with really small buffer cache).
Chris, so have you checked whether the plan_hash_values (and additionally the predicate sections of the plans) on each node are exactly the same - and the amount of IOs per execution these statements are the same on each node? (and if yes - what are the average IO wait event durations on different nodes?)
-- Tanel Poder Enkitec (The Exadata Experts) Training<http://blog.tanelpoder.com/seminar/> | Troubleshooting<http://blog.tanelpoder.com/> | Exadata<http://www.amazon.com/Expert-Oracle-Exadata-Apress/dp/1430233923> | Voicee App<http://voic.ee/> On Mon, Apr 22, 2013 at 11:29 PM, Alex Fatkulin <afatkulin_at_gmail.com<mailto:afatkulin_at_gmail.com>> wrote: You need "_serial_direct_read"=always On Mon, Apr 22, 2013 at 4:23 PM, <Christopher.Taylor2_at_parallon.net<mailto:Christopher.Taylor2_at_parallon.net>> wrote:Received on Mon Apr 22 2013 - 22:47:55 CEST
> I tried setting:
> "_serial_direct_read"=TRUE and that does not do it.
>
> --
Alex Fatkulin, http://afatkulin.blogspot.com Enkitec, http://www.enkitec.com -- http://www.freelists.org/webpage/oracle-l