IDS Forum

RE: Checkpoint duration too long sometimes--no fixed pattern [105 [1060]

Posted By:
Date:

Thanks everybody for sharing your thoughts on this and
providing the invaluable tips. I will be making the
changes over ther period of time and see the impact.
Very much sure its gonna help.

Thanks,

Vineet
--- "Simmons, Keith" <keith.simmons@bbslimited.co.uk>
wrote:
> Vineet
>
> It looks as though your dirty buffers are never
> reaching the 2% required to
> start the LRU Writes run 'onstat -R' a few times,
> especially just before a
> checkpoint, to see what percentage of buffers become
> dirty. Even 2% of
> 500000 buffers is 10000 which will take a while to
> write. Three ways to
> reduce the number of dirty buffers at checkpoint
> time, either reduce the
> overall number of buffers, reduce the LRU
> percentages or reduce the time
> between checkpoints. What are your cached
> percentages from onstat -p. Reduce
> the number of buffers until these start to decline
> and if this doesn't
> improve matters significantly then reduce LRU
> percentages to 1 and 0.
> A third alternative is to remove the responsibility
> for writing from the
> checkpoint by running onmode -B (undocumented,
> flushes all dirty buffers as
> a back-ground task) immediately before a checkpoint
> is due (see also a
> recent thread regarding this).
>
> Keith
>
> -> -----Original Message-----
> -> From: Vineet Mehr.... [mailto:vin_us@yahoo.com]
> -> Sent: Wednesday, April 30, 2003 9:52 PM
> -> To: ids@iiug.org
> -> Subject: Checkpoint duration too long
> sometimes--no fixed
> -> pattern [1054]
> ->
> ->
> ->
> -> Environment:
> ->
> ->
> -> Informix Dynamic Server 7.31 UD2 R1
> ->
> -> HP-UX 11.0
> ->
> -> As you can see below
> ->
> -> 10:44:50 Checkpoint Completed: duration was 0
> -> seconds.
> -> 10:59:59 Checkpoint Completed: duration was 0
> -> seconds.
> -> 11:15:08 Checkpoint Completed: duration was 0
> -> seconds.
> -> 11:30:17 Checkpoint Completed: duration was 0
> -> seconds.
> -> 11:45:26 Checkpoint Completed: duration was 0
> -> seconds.
> -> 12:00:53 Checkpoint Completed: duration was 19
> -> seconds.
> -> 12:16:02 Checkpoint Completed: duration was 0
> -> seconds.
> -> 12:31:34 Checkpoint Completed: duration was 23
> -> seconds.
> -> 12:46:44 Checkpoint Completed: duration was 0
> -> seconds.
> -> 13:01:54 Checkpoint Completed: duration was 1
> -> seconds.
> -> 13:17:05 Checkpoint Completed: duration was 2
> -> seconds.
> -> 13:32:15 Checkpoint Completed: duration was 0
> -> seconds.
> -> 13:47:24 Checkpoint Completed: duration was 0
> -> seconds.
> -> 14:02:33 Checkpoint Completed: duration was 1
> -> seconds.
> -> 14:17:43 Checkpoint Completed: duration was 1
> -> seconds.
> -> 14:32:54 Checkpoint Completed: duration was 0
> -> seconds.
> -> 14:48:03 Checkpoint Completed: duration was 0
> -> seconds.
> -> 15:03:13 Checkpoint Completed: duration was 2
> -> seconds.
> -> 15:18:23 Checkpoint Completed: duration was 0
> -> seconds.
> -> 15:35:08 Checkpoint Completed: duration was 97
> -> seconds.
> ->
> -> we have at times checkpoints of duration more
> than a
> -> minute. This is totally unacceptable in
> production
> -> environment.
> ->
> -> We are unable to diagnose a pattern for this. It
> could
> -> happen at any time throughout the day. I don't
> have
> -> any clues where to look for and what could be the
> -> possible reason for this behaviour.
> -> Here are the related checkpoint parameters which
> we
> -> have set in our environment for your reference.
> ->
> -> MULTIPROCESSOR 1 # 0 for
> -> single-processor, 1 for multi-processor
> -> NUMCPUVPS 5 # Number of user
> (cpu)
> -> vps
> -> SINGLE_CPU_VP 0
> ->
> ->
> -> BUFFERS 500000
> ->
> -> CLEANERS 128
> ->
> -> CKPTINTVL 900
> ->
> -> LRUS 128
> ->
> -> LRU_MAX_DIRTY 2
> ->
> -> LRU_MIN_DIRTY 1
> ->
> ->
> -> Also interesting most of the times we have 0 LRU
> -> writes in the system and only writes happen are
> the
> -> chunkwrites at the time of checkpoint.
> ->
> -> Fg Writes LRU Writes Chunk Writes
> -> 0 2 14620
> ->
> -> Are we hitting some kind of bug? Or doing
> something
> -> wrong.
> ->
> -> Any help on this is highly appreciated.
> ->
> -> Do let me know if you need more information.
> ->
> -> Thanks and regards,
> ->
> -> Vineet
> ->
> ->
> ->
> ->
> ->
> -> __________________________________
> -> Do you Yahoo!?
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> ->
>
>
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Messages In This Thread

• Problem updating Linked Table in MS Access
  Richard Spitz -- Thursday, 23 January 2003, at 12:22 p.m.
  • Re: Problem updating Linked Table in MS Access
    Mike Dunham-Wilkie -- Thursday, 23 January 2003, at 1:36 p.m.
    • RE: Checkpoint duration too long sometimes--no fixed pattern [105 [1060]
      Vineet Mehrotra -- Friday, 2 May 2003, at 3:02 p.m.
  • RE: Problem updating Linked Table in MS Access
    Spitz, Richard Dr. -- Monday, 27 January 2003, at 3:56 a.m.

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