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

  • From: Tanel Poder <tanel@xxxxxxxxxxxxxx>
  • To: Alex Fatkulin <afatkulin@xxxxxxxxx>
  • Date: Mon, 22 Apr 2013 23:45:11 +0300

_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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*Tanel Poder*
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On Mon, Apr 22, 2013 at 11:29 PM, Alex Fatkulin <afatkulin@xxxxxxxxx> wrote:

> You need "_serial_direct_read"=always
> On Mon, Apr 22, 2013 at 4:23 PM, <Christopher.Taylor2@xxxxxxxxxxxx> 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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