Re: Question - any parameter or hint to FORCE Physical Read (bypass buffer cache)

From: Tanel Poder <tanel_at_tanelpoder.com>
Date: Mon, 22 Apr 2013 23:45:11 +0300
Message-ID: <CAMHX9J+yVBLMzMTBwyTN0cwYjRj-7pz2AODrwGKGHaVX4z0jAw_at_mail.gmail.com>

_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?)

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On Mon, Apr 22, 2013 at 11:29 PM, Alex Fatkulin <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> wrote:

>

> > I tried setting:

> > "_serial_direct_read"=TRUE and that does not do it.

> >

> > --

> Alex Fatkulin,

> http://afatkulin.blogspot.com

>

> Enkitec,

> http://www.enkitec.com

>

>



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Received on Mon Apr 22 2013 - 22:45:11 CEST