Re: AIX Concurrent I/O for Oracle archive logs

  • From: "Rich Jesse" <rjoralist@xxxxxxxxxxxxxxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Wed, 26 May 2010 08:46:25 -0500 (CDT)

Hey Nuno,

> Allen, Brandon wrote,on my timestamp of 26/05/2010 2:06 AM:
>> Can anyone think of a good reason why Oracle?s archived redo logs
>> shouldn?t be placed on a non-buffered (concurrent or direct IO) file
>> system?  Oracle Support document 418714.1 specifically states NOT to use
>> DIO/CIO for file systems containing archive logs.    However, I have one
>> AIX system where my archive logs have been on a file system mounted with
>> CIO for years and I?ve never had any problems (and yes, I?ve
>> successfully used the logs for actual recovery).


> Above all: be very careful with the doco you find online.  There are perhaps
> two
> documents in the entire IBM tech lib that are relevant and pertinent for
> current
> versions of software and OS.

Does the "Tuning IBM AIX 5L for an Oracle Database" PDF (Google it -- my
copy has the intuitive filename of "9a46.pdf") qualify as one of these

My problem with the MOS article Brandon mentioned and the paper above is
their use of absolutes without regard to situation or consequences.  It's
like the warning that comes with the cooking instructions on my kids'
chicken nuggets:  "Space the nuggets apart -- Do NOT let them touch!"  What
if they do?  Will they explode?  Will they reanimate?  WHAT??!??!?

Same with the MOS article and the IBM paper I mentioned.  Is CIO mounting of
the archives going to slow something down?  Or perhaps potentially relieve
swap pressure on a system with low RAM and an auto-adjusting file cache,
resulting in an overall performance increase?

Without a definitive answer on the ramifications of the action/inaction, it
sounds like empirical evidence and a good DBA's best judgement are the key
tools.  Then again, they usually are...  :)



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