Re: large number of shared memory segments

Sean Kelsey wrote: > > IDS 7.24.UC5, HP9000 running HP-UX 11.0 > > We had an interesting situation last night where the server > un-surprisingly ) appeared to not accept any user requests from either > soctcp or shmem connections even though the engine was up and running and > was issuing checkpoints. We couldn't manually issue checkpoints either, the > terminal would freeze, and no onmode commands would work. Having ensured > that no processes were in critical sections, I eventually had to kill the > master oninit process using kill -11 ( -9 is a no no I know ). Ouch! > The onstat commands appeared to be working fine providing whatever stats we > wanted, one of which was the onstat -g seg which gave us about 32 additional > V segments each 8MB in size. Default sizes. > ( at this point alarm bells started to ring ). Good. > My problem, however, was that I didn't know of a way to trace back what > process ( or processes ) caused so many segments to be added in such a short > time - over a period of about 1 hour. > > Can any of you guys/galls point me in a few directions that I may need to > investigate so that if/when it happens again, I can narrow the search down > to a particular user/process AQAP. The only way you can get this sort of info is to monitor individual session's memory usage. Something like onstat -g ses. But of course, CATCHING the culprits is another story. Perhaps you can set up a cron job to store stats over a period of time. > I have already upped the SHMVIRTSIZE to 750MB ( from 500MB) and SHMADD to > 64MB ( from 8MB) to reduce the number of segments the next time it needs to > add them, and also implemented a script to raise the alarm if > 3 segments > get allocated. Good. > I must point out that this happened when there were relatively few ( ~300 ) > users on the system not running anything massive. > > I wait with baited breath. Try a breath mint. :-) Cheers, -- Mark. +----------------------------------------------------------+-----------+ |Mark D. Stock - Informix SA http://www.informix.com |//////// /| |mailto:mdstock@informix.com http://www.informix.com/idn |///// / //| |http://www.iiug.org +-----------------------------------+//// / ///| | Tel: +27 11 807 0313 |If it's slow, the users complain. |/// / ////| | Fax: +27 838250 2325 |If it's fast, the users keep quiet.|// / /////| |Cell: +27 83 250 2325 |Therefore, "No news: travels fast"!|/ ////////| +----------------------+-----------------------------------+-----------+