Re: disks for redo logs

From: hpuxrac <>
Date: Sun, 15 Feb 2009 16:42:17 -0800 (PST)
Message-ID: <>

On Feb 11, 2:26 pm, joel garry <> wrote:


> (and I would guess above) check out the ${ORACLE_SID}
> _lgwr*trc trace files, it spits out a message whenever log writes take
> more than .5 seconds or something, compare to your performance
> monitoring.  I was a bit surprised when I first noticed what's in
> those traces, haven't quite figured out how to translate that for
> management.  The surprising part was the size of writes versus the
> waits - apparently quite unrelated.  Which I guess makes sense if the
> waits are caused by other things than the log writes.
> I used to think having different volume groups would help, but I've
> been disabused of that notion.  Now I don't understand it at all.  SAN
> cache makes it all strange, too.

IO hiccups and "strange unrelated spikes" in IO response time in a SAN environment involves some aspect that Dante wrote about as far as I know. No knowledgeable SAN admin ever admits to knowing anything ( well rarely anyways ) relevant.

> But hey, if users aren't complaining, everything is peachy.  Right?

If it is log writes from a commit or rollback then any other transactions ( if any ) involved in any concurrency situations will be impacted ... but you know that already eh? Received on Sun Feb 15 2009 - 18:42:17 CST

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