RE: PARALLEL_EXECUTION_MESSAGE_SIZE
- From: "Gogala, Mladen" <MGogala@xxxxxxxxxxxxxxxxxxxx>
- To: "'zhuchao@xxxxxxxxx'" <zhuchao@xxxxxxxxx>, Oracle-L <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 5 Oct 2005 10:21:15 -0400
Yup. It's called "do not touch unless directed otherwise by Oracle technical
support personnel". It determines the
size of message interchanged by the query coordinator and slave processes.
Oracle did not publish the message allocation
methods, so by increasing the message size, you can drain your processes out
of message structures and cause virtual
deadlocks. I have few weeks of experience with Oracle and I've never seen
parallel messages cause any problems.
Remember, you should be tuning application, not an Oracle instance.
The instance tuning approach was originated by Bruce Ellis and Clay Prestia,
gurus of now dead but never quite forgotten
OS, which was in my opinion far superior to any present OS, with the
possible exception of zOS. The secret of performance,
according to Clay Prestia, was to do things from memory and not from disk. I
attended one of his classes in Bruxelles, Belgium,
in which he was teaching us to look at paging and working sets, I/O,
modified page writer (MPW sysgen parameters) and anything
but using a profiler. He was advocating "tuning system" approach, instead of
tuning program and even looking into the system
if and only if the problem application is waiting on the system service.
Bruce Ellis and Clay Prestia are spiritual fathers of
the venerable "method C" described in the "Optimizing Oracle Performance"
book by Cary Millsap & Jeff Holt.
--
Mladen Gogala
Ext. 121
_____
From: zhu chao [mailto:zhuchao@xxxxxxxxx]
Sent: Wednesday, October 05, 2005 7:43 AM
To: Oracle-L
Subject: PARALLEL_EXECUTION_MESSAGE_SIZE
hi, all
Have anyone noticed this parameter for oracle 9i? Document says max size
is 64KB-1, and actually oracle round it to 64K. But if I try another size
like 30k/60k, oracle does not change it. Anyone know the magic behind?
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