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

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!? > -> The New Yahoo! Search - Faster. Easier. Bingo. > -> http://search.yahoo.com > -> > > ******************************************************************************** ** > This message is sent in strict confidence for the > addressee only. It may > contain legally privileged information. The contents > are not to be disclosed > to anyone other than the addressee. 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