Re:RE: Parallel select, excessive IO and parallel_execution_message_siz

From: Laimutis.Nedzinskas@xxxxxx
To: oracle-l@xxxxxxxxxxxxx
Date: Tue, 1 May 2012 10:11:34 +0300

I've got a confirmation message size parameter has nothing to do with the
problem. The stop/start (db bounce or kill the query-run in again) was
responsible for return to normal execution.
Curently I am just making sure the bind variables passed into the query are
the same in both runs.
All else seems to be exactly the same - same plan, same plan hash value,
same optimizer environment (judging from v$sql), same workarea usage.
I've got a confirmation from my collegues they experienced a similar
problem before with PX. Kill/restart usually helped.
Wondering if anyone else had such experience ?


On Mon, Apr 23, 2012 at 7:23 AM, <Laimutis.Nedzinskas@xxxxxx> wrote:.
      Did anyone experience this phenomena of parallel select:

      select /*+parallel ( 2) */ went reading one segment like crazy - disk
      reads
      many times over the segment(table) size.
      The finding was supported by v$sql, v$sesstat and AWR reports.

      The plan was a hash join of two tables plus a filter (select from 2
      records
      table)

      After the parallel_execution_message_size was bumped to maximum (64k)
      and
      oracle server bounced the select completed within expected time and
      IO
      limits.

      Can parallel_execution_message_size affect IO (and time) of parallel
      select
      so drastically ?

      Thank you in advance, Laimis N


---------------------------------------------------------------------------------

Please consider the environment before printing this e-mail

--
//www.freelists.org/webpage/oracle-l

Re:RE: Parallel select, excessive IO and parallel_execution_message_siz

Other related posts: