Re: IDS 9.20
>From: "Neil Truby" <ntruby@netcomuk.co.uk> >Reply-To: "Neil Truby" <ntruby@netcomuk.co.uk> >To: informix-list@iiug.org >Subject: IDS 9.20 >Date: Mon, 14 Aug 2000 00:33:30 +0100 >Received: from [206.175.175.254] by hotmail.com (3.2) with ESMTP id >MHotMailBB60877800A6D82197E0CEAFAFFEF7660; Sun Aug 13 17:25:31 2000 >Received: (from majordom@localhost)by iiug.iiug.org (8.8.8+Sun/8.8.8) id >TAA23602;Sun, 13 Aug 2000 19:15:01 -0500 (CDT) >From owner-informix-list@iiug.iiug.org Sun Aug 13 17:30:16 2000 >Organization: (Posted via) GTS Netcom. >Message-Id: <8n7bde$dab$1@lyonesse.netcom.net.uk> >X-List-Gateway: comp.databases.informix >Sender: owner-informix-list@iiug.iiug.org >Precedence: bulk > >IDS 9.20 HC-2 on HP-UX 11.0. > >I posted a query a few days ago about performance degradation, but answered >it myself when I discovered a runaway select/update process caused the >issues. > >But having thought about it, and reproduced the issue with a sequential >scan/delete construct, I'm still not happy. I find it hard to believe that >a single query, however heavy duty, could freeze out other users to the >extent it did. When it was running it could take 20 seconds to build the >table list for a dbaccess->query-> info request - it was that bad. And >we're talking about an HP N4000 here - a seriously meaty machine. > >Could it be an IDS 9.20 thing, that a single query could have such an >impact? I can't remember it on7.x. Anyway, I'm going to do some >comparative testing. > >But, if anyone does know of any issues in this area, I'd love to know. If >youhave any dazzling insight could you copy it to neil.truby@londis.co.uk, >as I don't get to the newsgroup too frequently. Was it causing more than 4 memory segments? We're talking about an HP here -- a seriously brain damaged memory architecture. :-) ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
> Was it causing more than 4 memory segments? We're talking about an HP here > -- a seriously brain damaged memory architecture. Nah. S'not that. I've had my arse bitten by that one before.
When you say 4 memory segments, do you mean extents to the original shared memory segment ( SHMVIRTSIZE / SHMADD ) I ask because we have similar performance problems and noticed several ( 10 ish ) extents being allocated shortly after database startup. Obviously, we have not sized SHMVIRTSIZE correctly, but does this cause serious performance issues? ( It's also an HP - K class ) Regards Neil "Obnoxio The Clown" <obnoxio@hotmail.com> wrote in message news:8n8ddl$8g5$1@news.xmission.com... > > > > Was it causing more than 4 memory segments? We're talking about an HP here > -- a seriously brain damaged memory architecture. :-) > ________________________________________________________________________ > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com >
STRONGN wrote: > > When you say 4 memory segments, do you mean extents to the original shared > memory segment ( SHMVIRTSIZE / SHMADD ) > > I ask because we have similar performance problems and noticed several ( 10 > ish ) extents being allocated shortly after database startup. Obviously, we > have not sized SHMVIRTSIZE correctly, but does this cause serious > performance issues? > > ( It's also an HP - K class ) Oh yes. The HP/PA architecture ONLY accesses shared memory through four special purpose registers. If you have to access more than four in an application the registers thrash the addresses and the machine grinds to a crawl. It is VERY important to increase SHMVIRTSIZE to include any additional virtual segments that get allocated beyond the first. In many cases the improvement is so dramatic it is worth kicking your users off to restart the engine with the larger SHMVIRTSIZE. Art S. Kagel > Regards > Neil > > "Obnoxio The Clown" <obnoxio@hotmail.com> wrote in message > news:8n8ddl$8g5$1@news.xmission.com... > > > > > > > > Was it causing more than 4 memory segments? We're talking about an HP here > > -- a seriously brain damaged memory architecture. :-) > > ________________________________________________________________________ > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > >