Re: Best Tune for Online 5.02

In article <5hu65h$9mr@cssun.mathcs.emory.edu>, Serafim Fonseca <inf@dpx20.growela.pt> writes >Hello, > >I have an Informix Online 5.02.UC6 installation running on a >RISC6000 with 128MB Ram, with about 30 users. >The production database is about 400MB. >I'm having performance problems. Could someone suggest me some >tunning tips. >The config is as follows: Tuning a database requires feedback. You need to look at the various tbstat listings to find out how the system is performing. ># Root Dbspace Configuration ># Physical Log Configuration > >PHYSDBS rlv02 # Name of dbspace that contains physical log >PHYSFILE 10240 # Physical log file size (Kbytes)Look at tbstat -m. Is the database checkpointing more frequently than once every 300 seconds at busy times? If so, think about making the physical logfile bigger. ># Logical Log Backup Tape Device > >LTAPEDEV /dev/null # Logical log tape device pathname >LTAPEBLK 16 # Logical log tape block size (Kbytes) >LTAPESIZE 10240 # Max amount of data to put on log tape (Kbytes)You really should be copying your logical logs to tape in case you need to recover! You're brave - or foolhardy - if you don't. ># Shared Memory Parameters > >RESIDENT 0 # Forced residency flag (Yes = 1, No = 0)>USERS 70 # Maximum number of concurrent user processes >TRANSACTIONS 70 # Maximum number of concurrent transactions >LOCKS 50000 # Maximum number of locksThat's a lot of locks - but it's not expensive in memory. >BUFFERS 6144 # Maximum number of shared memory buffersIf you can have more buffers, you'll get better performance - as long as you don't start swapping in UNIX. >TBLSPACES 700 # Maximum number of active tblspaces >CHUNKS 8 # Maximum number of chunks >DBSPACES 8 # Maximum number of dbspaces and blobspaces >PHYSBUFF 1536 # Size of physical log buffers (Kbytes) >LOGBUFF 1024 # Size of logical log buffers (Kbytes)>LOGSMAX 12 # Maximum number of logical log files >CLEANERS 3 # Number of page-cleaner processesYou can sometimes make checkpoints faster if you have more page cleaners, but I've been told that more cleaners than the number of disks in your system doesn't help. >SHMBASE 0x30000000 # Shared memory base address >CKPTINTVL 300 # Checkpoint interval (in seconds)If performance is more important than resilience, switch your databases to buffered logging and increase the checkpoint interval - then the write buffered percentage in the tbstat -p listing gets higher. Both the read and write percentages should get into the low 90s. >LRUS 8 # Number of LRU queues >LRU_MAX_DIRTY 60 # LRU modified begin-cleaning limit (percent) >LRU_MIN_DIRTY 50 # LRU modified end-cleaning limit (percent)If the checkpoint is taking too long (the system "hangs" for a while every 5 minutes), move these percentages down to 50 and 40 respectively. >LTXHWM 80 # Long TX high-water mark (percent) >LTXEHWM 90 # Long TX exclusive high-water mark (percent)> >TIA >Serafim Fonseca > Hope the above is useful. Informix do some very good training about all this, if you can justify the expense. But really, you need to find out about "tbstat" and use it! -- Peter R Wotherspoon