IDS Forum

RE: AW: Tuning Checkpoints

Posted By: Edcel Barcena
Date: Sunday, 9 December 2007, at 8:44 p.m.

In Response To: AW: Tuning Checkpoints (Andreas.KUTSCHE@spar.at)

Hi Andreas,

You've brought up an interesting point regarding "degenerated attached indices and insert statements blocking a checkpoint for over a minute". We're currently having the same problem and the recommendation I got from IBM Informix Support was to recreate the index as detached.

Right now, there's no way we'll be able to do that as our users don't approve of a downtime and we're at IDS9.40 which doesn't have the facility to do online index rebuild(drop/create). Based on your experience, is there any other way we can reduce those long checkpoints?

Thanks & Regards,
Edcel

> To: ids@iiug.org
> From: andreas.kutsche@spar.at
> Subject: AW: Tuning Checkpoints [10657]
> Date: Fri, 7 Dec 2007 16:41:32 -0500
>
> Hi,
>
> 128 LRUs with 350000 Buffers and LRU_MAX_DIRTY 0.5 should be far enough and
> give you checkpoints between one and two seconds.
>
> Is your IO performance okay (KAIO an how many CPU VPs or when using normal IO
> how many AIO VPs)? Does your SAN storage have a write cache (battery
> buffered)?
>
> Maybe you may want to try lower LRU-numbers. SAP suggests LRU numbers = CPU
> VPs. In most cases that seems to work, too.
>
> Did you monitor your checkpoints? Run onstat - in an endless loop and as long
> as it shows a checkpoint get the dirty buffers (onstat -R) and the threads in
> critical sections (onstat -u | grep X) - maybe you don't have a problem with
> the dirty buffers but with sessions in critical sections which block the
> checkpoint.
> We had some problems with (degenerated) attached indices and insert statements
> - sometimes they blocked a checkpoint for over a minute.
>
> Regards,
> Andreas Kutsche
>
> >
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> -------------------------------------------
> -----Ursprüngliche Nachricht-----
>
> > Von: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] Im Auftrag von
> > ALICE BENNETT
> > Gesendet: Freitag, 07. Dezember 2007 15:59
> > An: ids@iiug.org
> > Betreff: Tuning Checkpoints [10650]
> >
> > I need some help getting checkpoints durations lowered. We are running
> > informix 9.4. I have been working with Informix Tech support and it has
> > gotten
> > some better but it is not as good as it should be. We have been adjusting
> > BUFFERS, LRUS, CLEANERS, LRU_MAX_DIRTY, and LRU_MIN_DIRTY.
> >
> > BUFFERS = 350000
> > LRUS = 128
> > CLEANERS = 127
> > LRU_MAX_DIRTY = .5
> > LRU_MIN_DIRTY = .25
> >
> > After the last changes we made, LRU writes is now lower than chunk writes
> > for
> > the first time.
> >
> > Our checkpoints have ranged up to 7 seconds and sometimes higher. Anyone
> > have
> > any ideas of what else we can look at?
> >
> > HP GL380G5 servers
> > 32Gb Memory
> > (2) quad core Processors
> > The dbspaces are located on Compellent SAN fiber channel drives RAID level
> > 10
> > (striped and mirrored).
> >
> >
> > **************************************************************************
> > *****
> > Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>

Messages In This Thread

• Tuning Checkpoints
  ALICE BENNETT -- Friday, 7 December 2007, at 9:58 a.m.
  • Re: Tuning Checkpoints
    Art S. Kagel (Oninit LLC) -- Friday, 7 December 2007, at 10:46 a.m.
    • AW: Tuning Checkpoints
      Andreas.KUTSCHE@spar.at -- Friday, 7 December 2007, at 4:45 p.m.
    • AW: Tuning Checkpoints
      Andreas.KUTSCHE@spar.at -- Tuesday, 11 December 2007, at 5:26 a.m.
      • Re: AW: Tuning Checkpoints
        Art S. Kagel (Oninit LLC) -- Tuesday, 11 December 2007, at 12:49 p.m.
  • AW: Tuning Checkpoints
    Andreas.KUTSCHE@spar.at -- Friday, 7 December 2007, at 4:41 p.m.
    • RE: AW: Tuning Checkpoints
      Edcel Barcena -- Sunday, 9 December 2007, at 8:44 p.m.
      • AW: AW: Tuning Checkpoints
        Andreas.KUTSCHE@spar.at -- Monday, 10 December 2007, at 4:12 a.m.
      • Re: RE: AW: Tuning Checkpoints
        ALICE BENNETT -- Monday, 10 December 2007, at 2:58 p.m.
        • Re: AW: Tuning Checkpoints
          Art S. Kagel (Oninit LLC) -- Monday, 10 December 2007, at 3:10 p.m.
          • AW: AW: Tuning Checkpoints
            Andreas.KUTSCHE@spar.at -- Tuesday, 11 December 2007, at 3:40 a.m.
            • Re: AW: AW: Tuning Checkpoints
              Madison Pruet -- Tuesday, 11 December 2007, at 9:52 a.m.
            • Re: AW: AW: Tuning Checkpoints
              Art S. Kagel (Oninit LLC) -- Tuesday, 11 December 2007, at 12:47 p.m.
        • RE: RE: AW: Tuning Checkpoints
          Pankaj Patel -- Monday, 10 December 2007, at 3:45 p.m.
        • AW: RE: AW: Tuning Checkpoints
          Andreas.KUTSCHE@spar.at -- Tuesday, 11 December 2007, at 3:30 a.m.
  • Re: Tuning Checkpoints
    NORMA JEAN SEBASTIAN -- Saturday, 8 December 2007, at 6:05 p.m.

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