Re: Checkpoints taking to long!!

I agree your part of decreasing MIN & MAX_DIRTY but not the part of increasing CKPTINTVL. During checkpoint the db server will use chunk write which is averagely more efficient than LRU write. So increase the number of buffer cleaners could help in this case. Double the CLEANERS parameter and see. Increase the LRU accordingly also helps. Dong >From: "Thomas J. Girsch" <tgirsch@iname.com> >Reply-To: "Thomas J. Girsch" <tgirsch@iname.com> >To: informix-list@iiug.org >Subject: Re: Checkpoints taking to long!! >Date: Wed, 24 Mar 1999 09:04:11 -0500 > >Two things I see: you can decrease your MIN and MAX_DIRTY a lot more than >that. On our systems we use 2 and 5, respectively. Some we have to go all >the way down to 1 or 2. If you increase the number of LRUs, it may help, >but I doubt it; we have about that many LRUs with double the space. > >Another thing you might try, though counter-intuitive, would be to INCREASE >the value of CKPTINTVL. The idea becomes that if there's more time between >checkpoints, the page cleaners have more time to "catch up" before a >checkpoint, and there's less to do at checkpoint time. This only works if >your checkpoints are typically occurring at CKPTINTVL (not forced by the >physical log getting full). Check how far apart your checkpoints are in >order to confirm this. The downside to this is that in the event of a >crash, it will take longer to get through physical/logical recovery. > >If your checkpoints are happening more frequently than CKPTINTVL, you may >consider increasing the size of your physical log. > >Remember, if you try any of these suggestions, try them one at a time, so >that you can see how each change affects the system. > >HTH, > >- Tom Girsch > tgirsch@iname.com >bridget wrote in message <36F82B39.C6D6833E@auckland.ac.nz>... >>Hi >> >>I've run into a problem with the checkpoints on my production system - >>they used to be all around 0 seconds long with the occasional 3 second >>checkpoint - now they have increased to more like 10-15 seconds average >>with a top of 20 seconds. We are running 730UC5 on a Sequent Box with 8 >> >>CPU dedicated to the database and 40 gig of mirrored space. >> >>Below are the settings in my onconfig file - I have decreased the >>max_dirty and min_dirty to see if it makes any difference, it didn't. >> >>Should I increase the number of LRU's and decrease the size of the >>logs?. Any ideas would be more than welcome. >> >> >># Shared Memory Parameters >> >>LOCKS 3000000 # Maximum number of locks >>BUFFERS 60000 # Maximum number of shared buffers >>NUMAIOVPS # Number of IO vps >>PHYSBUFF 32 # Physical log buffer size (Kbytes) >>LOGBUFF 32 # Logical log buffer size (Kbytes)>>LOGSMAX 40 # Maximum number of logical log files >>CLEANERS 8 # Number of buffer cleaner processes >>SHMBASE 0x10000000 # Shared memory base address >>SHMVIRTSIZE 144000 # initial virtual shared memorysegment >> >>size >>SHMADD 16000 # Size of new shared memory segments >>(Kbytes) >>SHMTOTAL 0 # Total shared memory (Kbytes). >>0=>unlimited >>CKPTINTVL 300 # Check point interval (in sec) >>LRUS 16 # Number of LRU queues >>LRU_MAX_DIRTY 40 # LRU percent dirty begin cleaninglimit >> >>LRU_MIN_DIRTY 35 # LRU percent dirty end cleaning limit >>LTXHWM 50 # Long transaction high water mark>>percentage >>LTXEHWM 60 # Long transaction high water mark >>(exclusive) >>TXTIMEOUT 0x12c # Transaction timeout (in sec) >>STACKSIZE 32 # Stack size (Kbytes)>> >> >>thanks Bridget >> >> >> > > Get Your Private, Free Email at http://www.hotmail.com