Re: System tuning

On Tue, 26 Mar 1996, Dave Kosenko wrote: > Informix Sysadmin wrote: > > MULTIPROCESSOR 1 > > NUMCPUVPS 2 > > SINGLE_CPU_VP 0> > As someone else has already pointed out, on a 2-proc box, you may find > better performance is achieved by tuning OnLine as though it were on a > uniprocessor. This is especially true if the box is not dedicated to > being a database server. I realised that what we had been doing is setting NUM, and SINGLE, but not fiddling MULTI....Have now set whole shebang to ONE processor. Seems to be snappier. > > > NUMAIOVPS> > The default value for NUMAIOVPS is 2*chunks, if I recall. That may be more > than you need, esp. if a chunk <> disk. More don't usually hurt performance, > as they just wind up idle and swapped out. When we dropped to single proc, it dropped this to 2. Seems like enough. > > CKPTINTVL 300 > I'd say this is low, but if you had not been seing problems with it > before, you shouldn't now. For kicks, we upped it to 600 > > > RA_PAGES > > RA_THRESHOLD> > If you are doing a fair amount of read i/o, you probably want to set > these. The default values are quite low (like 4 or 8, I forget offhand). > Set these at maybe 64 and 32, and it should help for i/o heavy activity. When we went to single proc, it set it to 4. Latest attempt has set it up to 32, and THRESH to 16 Not sure yet what implications. > > PDQPRIORITY 0 > > If you have fragmented your tables at all, you may want this at 1 at > least; that will give you parallel scans. Even on a uni or 2 proc system, > parallel scans can be a win. We have no fragmented tables....are looking at that as a possibility as well (on the side) > > OPTCOMPIND 1> > Be sure that your index accesses are truly faster. In some cases, a hash join > may be the better choice. It is at least worth a few tests to be certain. Suggestions for testing this? Thanks to all presently, as the system is almost back to a bearable speed. It's been a long 3 weeks. B. ------------------------------------------------------------------------- |Brian P. Hampson Internet : brian@asl-labs.bc.ca | |System Administrator, Air(2m/70cm): VE7NNW | |Analytical Service Labs Fidonet : Brian Hampson 1:153/733| |Vancouver, BC | |+604-253-4188 | | Specialists in Environmental Chemistry | | | ------------------http://www.asl-labs.bc.ca/-----------------------------