Questions about values of memory in onconfig

Hi all again. I'm working with a 7.31 UC2 with HP-UX 10.20 I'm tunning the memory values of onconfig, exactly SHMVIRTSIZE and SHMADD. We have recently change to this version of Informix and who installed us this version changed the values of SHMVIRTSIZE and SHMADD (they was set to 240000 and 30000). He said that they was too high for us. Now I have SHMVIRTSIZE set to 200000 and SHMADD set to 8000 (its original value). Since Monday I changed SHMVIRTSIZE from 140000 to 200000 (a lot of segments were created daily). I suppose that a big number of new segments is very bad for the performance... is it right? It's better a low value to SHMADD or not? Is it possible to get the process that caught the additional segments? Perhaps the process that caught the segment didn't finish ok or perhaps Informix doesn't free the additional segments when he doesn't need them. If I can get the process perhaps I can free the segment but, is it possible to free a segment with blkused <> 1? I know that 'onmode -F' free the segments with blkused = 1. Thanks in advance !!! DJMoralesM dmorales@giro.es

In article <7r8h5o$mit$1@news.xmission.com>, "Diego Morales"<dmorales@giro.es> wrote: > > > Hi all again. > > I'm working with a 7.31 UC2 with HP-UX 10.20 > > I'm tunning the memory values of onconfig, exactly SHMVIRTSIZE and > SHMADD. > > We have recently change to this version of Informix and who installed > us this version changed the values of SHMVIRTSIZE and SHMADD > (they was set to 240000 and 30000). He said that they was too high for us. > > Now I have SHMVIRTSIZE set to 200000 and SHMADD set to 8000 > (its original value). Since Monday I changed SHMVIRTSIZE from 140000 > to 200000 (a lot of segments were created daily). I suppose that a big > number of new segments is very bad for the performance... is it right? Yes, absolutely. Try to keep all virtual memory in one segment. > > It's better a low value to SHMADD or not? It depends on your system. For example, if just loaded large amount of data and need to build indexes, it's better to allocate one big segment (especially, if indexes are builded with PDQ turned on). But if during normal processing your system only sometimes needs virtual memory, set SHMADD to something like 16000 or 32000. I repeat, everything depends on your system and daily activity. > > Is it possible to get the process that caught the additional segments? > Perhaps the process that caught the segment didn't finish ok or perhaps > Informix doesn't free the additional segments when he doesn't need them. > If I can get the process perhaps I can free the segment but, is it possible > to > free a segment with blkused <> 1? > I know that 'onmode -F' free the segments with blkused = 1. > Yes, onmode -F is right thing. If this doesn't help, use 'ipcrm' unix command. -- With best regards, Yuri Dovgart, SAP R/3, Informix consultant, "Telecominvest" company. E-mail y_dovgart@tci.ukrtel.net Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't.

Diego Morales wrote: > > Hi all again. > > I'm working with a 7.31 UC2 with HP-UX 10.20 > > I'm tunning the memory values of onconfig, exactly SHMVIRTSIZE and > SHMADD. > > We have recently change to this version of Informix and who installed > us this version changed the values of SHMVIRTSIZE and SHMADD > (they was set to 240000 and 30000). He said that they was too high for us. Obviously the fella was wrong, eh? > Now I have SHMVIRTSIZE set to 200000 and SHMADD set to 8000 > (its original value). Since Monday I changed SHMVIRTSIZE from 140000 > to 200000 (a lot of segments were created daily). I suppose that a big > number of new segments is very bad for the performance... is it right? Correct. Fewer segments are better and on HP more than one extra segment is performance DEATH! (HP PA RISC CPUs have only 4 special purpose registers for shared memory base address handles so more will cause these registers to thrash killing throughput). > It's better a low value to SHMADD or not? Looks like it and looks like you have to increase SHMVIRTSIZE again also. Make sure to fold ALL additional virtual segments that hang around for any extended period or which show up again after you remove them with onmode -F into SHMVIRTSIZE and to police for additional segments you can free with aggressive diligence. > Is it possible to get the process that caught the additional segments? Very hard. Usually sessions doing extensive sorting, like update stats or ORDER BY without indexes. > Perhaps the process that caught the segment didn't finish ok or perhaps > Informix doesn't free the additional segments when he doesn't need them. It does not, that is why the onmode -F option exists. > If I can get the process perhaps I can free the segment but, is it possible > to > free a segment with blkused <> 1? > I know that 'onmode -F' free the segments with blkused = 1. Sometimes if the additional used pages are also server overhead the server will move those to another segment and release the new segment. It's worth a try. Art S. Kagel