Re: Informal poll: What's your avg redo write time?

  • From: Jeremy Schneider <jeremy.schneider@xxxxxxxxxxxxxx>
  • To: rjoralist3@xxxxxxxxxxxxxxxxxxxxx
  • Date: Thu, 19 Feb 2015 16:29:10 -0500

if you're troubleshooting a LGWR issue, you might see if this script
gives you some additional useful info - it helped me a bunch with some
LGWR related troubleshooting last year.

https://github.com/fidelinho/SAP_Note_1438410_V49/blob/master/SystemStatistics_LGWR.txt

i haven't looked at kyle's script to see what exactly it's doing - but
assuming it's just showing the time for write calls to the storage,
then my take would be that <1ms shouldn't be problematic on a typical
system.  timings are going to depend greatly on what sort of storage
people are on.  what kind of storage are you on?

-J

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On Thu, Feb 19, 2015 at 4:10 PM, Rich Jesse
<rjoralist3@xxxxxxxxxxxxxxxxxxxxx> wrote:
> Hey all,
>
> In 11.2.0.3 on AIX 7.1, I'm tracing down an issue on an SR and stumbled into
> the world of LGWR.  It's causing blocking locks (falsely being reported, I
> believe) when stressed, so I'm looking at LGWR performance.
>
> Using Kyle Hailey's average log write time query at the bottom of -- NOTE:
> TUNING PACK LICENSE REQUIRED --
> http://www.oaktable.net/content/lgwr-redo-write-times-log-file-parallel-write
> my average is about 0.52ms with 90% of all between 0.4ms and 0.6ms, and
> another 8.4% at 0.7ms.
>
> Knowing that there's over-committing going on, I'm thinking that 0.52ms
> isn't my issue, but what are other folks getting?
>
> TIA!
> Rich
>
> p.s.  Testing HTML formatting -- apologies if this message doesn't look like
> it should!
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