Re: How to change oracle process scheduling policy in AIX5L?

  • From: Tanel Poder <tanel@xxxxxxxxxx>
  • To: neil_chandler@xxxxxxxxxxx
  • Date: Wed, 3 Nov 2010 23:59:28 +0200

...but there's a case for *fixing* priorities of Oracle procs so
long-running processes wouldn't end up with lower priority as the scheduler
thinks they're non-interactive CPU hogs. When this happens to LGWR, you'll
have long log file sync's all over the place even though the IOs finish

Also, another class of problems is priority inversion, where a latch or
Oracle mutex holder process with lower prio than others gets pre-empted - it
won't get back onto CPU to release the lock for a while as everyone else is
burning CPU spinning on the same lock... this is especially bad when you run
an oracle version where failed mutex gets never sleep, but get into a spin &
yield loop... you'll end up having huge CPU spikes and *cursor: pin
s*waits. I wrote about one case like that here:

You can set system-wide scheduler behavior on AIX using schedo command and
there's a setting which will give you fixed priorities:

However I've never used it, never seen anyone using it so have no idea how
well it works (and what else breaks)

Tanel Poder
*New virtual conference!*

On Sat, Oct 16, 2010 at 4:47 PM, Neil Chandler <neil_chandler@xxxxxxxxxxx>wrote:

> What problem are you trying to solve be changing the Oracle process
> priority? Re-nicing generally unbalances the Oracle system and causes
> problems.
> Regs
> Neil Chandler.
> sent from my phone
> On 12 Oct 2010, at 12:26, "Leyi Zhang (Kamus)" <kamusis@xxxxxxxxx> wrote:
> > Hi, Gurus
> >
> > We need to set a fixed process priority in AIX5.3 for Oracle Database
> > processes, just like enable SCHED_NOAGE for Oracle Database in HP-UX.
> > We know we can use renice command to set process priority manually,
> > but I don't think this is the only solution on AIX.
> >
> > Any suggestion is appreciated.
> >
> > --
> > Kamus <kamusis@xxxxxxxxx>
> >
> > Visit my blog for more :
> > Join ACOUG:
> > --
> >
> >
> >
> >
> --

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