Messages in this thread | | | From | justinf@us ... | Date | Fri, 27 Aug 1999 13:10:33 -0400 | Subject | Re: Oracle and Linux (hand in hand) |
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> I've read tuning tips wrt Oracle on Linux. Most say to increase SHMMAX and the > semaphores. I ask you this, what _real_ difference does it make? Am I going > to be able to see the difference on a VA3500 (quad pent III 550,512M RAM)? I'd > much rather use a stock kernel, but I'll hack for the good of my users.
Actually, the difference is very real, and you will probably be unable to run Oracle without making changes. The speed of your processor or the amount of RAM you have don't matter much here. Increasing kernel parameters are necessary to meet the System V IPC requirements that Oracle makes in order to run. If you make heavy use of Oracle--large tables, heavy usage, etc. you will probably find the need to increase some of these parameters even further. It all depends on how Oracle was written, how it handles IPC shortages, and what other programs you may be running that have IPC requirements.
Don't think of this as "hacking" your kernel. It's very common for UNIX sysadmins to have to tune kernel parameters to suit their users and the applications they run. I work on software which runs across lots of UNIX platforms (Solaris, AIX, HP-UX, Digital UNIX and others--Linux coming soon) and we frequently tell people to bump up kernel parameters for System V IPC. In my experience, AIX is the only UNIX which avoids all of this (SEM*, SHM*, MSG*) by handling it dynamically and transparently. The only quirk is that shared memory on AIX behaves a bit differently than on other UNIX platforms (look up the EXTSHM=ON environment variable on the web and you'll see what I mean).
While we're on the topic of IPC, does anybody have information on the state of POSIX.1b IPC (a la Stevens' UNPv2) in Linux? I did a bit of looking around just now and the best piece of information I could find was an old (1996) l-k note by Ulrich Drepper. Will there be a new set of tuning parameters to deal with or is that going to remain a "feature" of System V IPC only?
Cheers,
Justin T. Fries MQSeries Support Raleigh, North Carolina "Just three miles west of the Angus Barn"
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