RE: Problem with Long Checkpoints

I observed the following ... The checkpoint interval is 3000 seconds but checkpoints occur at less than 50 minutes. What is causing the quick checkpoint? I suspect that the physical log may be too small for that instance. Despite the checkpoint duration, you do not have many chekcpoint waits. With 20 AIOVPS you are presumably not running KAIO. How many chunks do you have? (2 AIOVPS per chunk). Can you change to KAIO? At the time of the checkpoint, what is needed to do? Do some instances have *longer* transactions than other instances? Are all instances similar in requirements and performance? Is there an IO problem on some instances at checkpoint time? Are some machine(s) more heavily loaded than others, and does that correspond to the instances with longer duration checkpionts? What is the effect of increasing NUMAIOVPS ? What is the effect of increasing LRUs and CLEANERS ? HTH Murray Wood -----Original Message----- From: Jeffrey Screws [SMTP:jeff_screws@yahoo.com] Sent: Wednesday, June 02, 1999 6:32 AM To: informix-list@iiug.org Subject: Problem with Long Checkpoints Hello, I have a problem with long checkpoint durations on some of my systems. Let me describe my environment. HW Environment: 7 HP 9000 K460 boxes w/ HP-UX 10.20 768mb or 1 gig of ram on each box 16 to 24 - 2.1 gb disks on each box depending on the number of Informix instances. Each instance has 10 dbspaces on only 2 mirrored pairs(4 disks in total). I'm sure this is at least part of the problem. But I'm sure there is some tuning the can help? DB Environment 1 to 4 instances on each box. The database is identical on each instance, (except for the contents of course!), and is roughly 4 gb is total size. Theses are by no stretch large databases! All storage is mirrored using HP LVM mirroring. Each instances probably has an average of 30 users hitting them 24x7. The application runs on the box also, so each user is telnetting in and running the 4GL app locally through shared memory connections. Here is the problem. On the best performing db instance the checkpoint duration is 2 or 3 seconds at every CKPTINTVL. On the worst performing instance the duration is usually around 8 or 9 seconds and sometimes up to 25 seconds. I am including all the info that I saw Art Kagel ask of someone a few days ago. Hope this isn't tooooooo much info. All suggestions welcome(and very much needed!) Thanks....Jeff S. INFORMIX-OnLine Version 7.24.UC5 -- On-Line -- Up 4 days 11:53:14 -- 192072 Kbytes Configuration File: /informix/etc/onconfig_lff #************************************************************************** # # INFORMIX SOFTWARE, INC. # # Title: onconfig.std # Description: INFORMIX-OnLine Configuration Parameters # #************************************************************************** # Root Dbspace Configuration ROOTNAME rootdbs # Root dbspace nameROOTPATH /links/ROOTDBS_LFF # Path for device containing root dbspace ROOTOFFSET 0 # Offset of root dbspace into device (Kbytes) ROOTSIZE 128000 # Size of root dbspace (Kbytes) # Disk Mirroring Configuration Parameters MIRROR 0 # Mirroring flag (Yes = 1, No = 0) MIRRORPATH # Path for device containing mirroredroot MIRROROFFSET 0 # Offset into mirrored device (Kbytes) # Physical Log Configuration PHYSDBS phylog # Location (dbspace) of physical log PHYSFILE 25000 # Physical log file size (Kbytes) # Logical Log Configuration LOGFILES 30 # Number of logical log files LOGSIZE 10000 # Logical log size (Kbytes) # Diagnostics MSGPATH /informix/online.log_lff # System message log file path CONSOLE /dev/console # System console message path ALARMPROGRAM /usr/local/publix/publix.infx_alarm # System Archive Tape Device #TAPEDEV /dev/null TAPEDEV /dev/rmt/0m # Tape device path #TAPEDEV /bu_lff/ontape_post_reorg.lff # Tape device path TAPEBLK 16 # Tape block size (Kbytes) TAPESIZE 5000000 # Maximum amount of data to put on tape (Kbytes) # Log Archive Tape Device LTAPEDEV /bu_lff/log.lff # Log tape device path #LTAPEDEV /dev/rmt/0m # Log tape device path LTAPEBLK 16 # Log tape block size (Kbytes) LTAPESIZE 5000000 # Max amount of data to put on log tape (Kbytes) # Optical STAGEBLOB ,1 # INFORMIX-OnLine/Optical staging area # System Configuration SERVERNUM 0 # Unique id corresponding to a OnLineinstance DBSERVERNAME onlineipc_lff # Name of default database server DBSERVERALIASES onlinetcp_lff # List of alternate dbservernames NETTYPE ipcshm,1,100,CPU # Override sqlhosts NETTYPE soctcp,1,75,NET # Override sqlhosts DEADLOCK_TIMEOUT 300 # Max time to wait of lock indistributed env. RESIDENT 1 # Forced residency flag (Yes = 1, No = 0) MULTIPROCESSOR 1 # 0 for single-processor, 1 formulti-processor NUMCPUVPS 4 # Number of user (cpu) vps SINGLE_CPU_VP 0 # If non-zero, limit number of cpu vpsto one NOAGE 0 # Process aging AFF_SPROC 0 # Affinity start processor AFF_NPROCS 0 # Affinity number of processors # Shared Memory Parameters LOCKS 300000 # Maximum number of locks BUFFERS 60000 # Maximum number of shared buffers NUMAIOVPS 20 # Number of IO vps PHYSBUFF 260 # Physical log buffer size (Kbytes) LOGBUFF 32 # Logical log buffer size (Kbytes)LOGSMAX 50 # Maximum number of logical log files CLEANERS 50 # Number of buffer cleaner processes SHMBASE 0x0 # Shared memory base address SHMVIRTSIZE 48000 # initial virtual shared memory segmentsize SHMADD 16384 # Size of new shared memory segments (Kbytes) SHMTOTAL 650000 # Total shared memory (Kbytes). 0=>unlimited CKPTINTVL 3000 # Check point interval (in sec) LRUS 50 # Number of LRU queues LRU_MAX_DIRTY 2 # LRU percent dirty begin cleaninglimit LRU_MIN_DIRTY 1 # LRU percent dirty end cleaning limit LTXHWM 40 # Long transaction high water markpercentage LTXEHWM 50 # Long transaction high water mark (exclusive) TXTIMEOUT 0x12c # Transaction timeout (in sec) STACKSIZE 48 # Stack size (Kbytes) # System Page Size # BUFFSIZE - OnLine no longer supports this configuration parameter. # To determine the page size used by OnLine on your platform #