Shared Memory Woes

Post #19,475 by gdaustin 11/26/01 9:29:46 PM Reply	Shared Memory Woes I'm having a devil of a time getting shared memory/message queues/semaphores configured on Red Hat 7.1 to run DB2 for Linux. It seems that we keep running out of "shared resources" (that's the message from DB2). We have increased the shared memory segment size multiple times, but it seems that there's a 32 meg limit per segment ( I don't know if this is the problem... ). I don't seem to be able to find anywhere info on semaphores and message queues. When I do IPCS, DB2 has multiple shared memory segments open, 2 32 meg segments, plus a 10 meg, plus a 7 meg, plus a 4 meg, 1 meg and lots more. There are about 50 semaphores in the list, as we as about 20 message queues. We also have an HP box, and have all this configured and running perfectly, per IBM's documentation. However, we seem to be coming up really short on RH 7.1. I'll post some messages to the DB2 board and look in the forum info to see if I can find a solution, but we're just about to throw out Linux for HP/UX, simply because our database runs great on HP/UX and chokes on Linux. \t Glen Austin "If you can't be kind, at least have the decency to be vague..."
Post #19,477 by Another Scott 11/26/01 10:29:52 PM Reply	Are you overloading DB2 "Personal"? Hi Glen, I'm no expert, so take this with a grain of salt... [link\|http://www-4.ibm.com/cgi-bin/db2www/data/db2/udb/winos2unix/support/v7pubs.d2w/en_main\|This] page at IBM lists various sets of documents for DB2 v7.x. It only lists "DB2 Personal Edition for Linux". Is there some Extended Edition or something similar for Linux now? Perhaps you're running into some capacity limits in that version which have little or nothing to do with tuning Linux. There are links to their troubleshooting pages [link\|http://www-4.ibm.com/cgi-bin/db2www/data/db2/udb/winos2unix/support/techlib.d2w/report\|here]. You've probably checked into these things already, but in case you haven't I thought I'd try to be another set of eyes searching for things... Best of luck. Cheers, Scott.
Post #19,768 by gdaustin 11/29/01 11:49:05 PM Reply	Re: Are you overloading DB2 "Personal"? DB2 Personal and DB2 Enterprise are the same, except that Personal does not allow remote (sockets) data connections. We found the problem. We are not running out of shared memory, but shared memory HANDLES! I found a page on the IBM website which describes a process to change the number of bits which represent the number of memory handles in the kernel. I think, by default, there are 32 or 64? The note describes changing this #define for more bits, then recompile the kernel. Apparently, the 2.4 kernel eliminates this constraint (I'm running RH 7.1?), but the current version of DB2 can't exploit it. So now, we've redefined our Linux DB config down to the minimum we can get away with to do our development and testing. Over time, we'll be moving this code to HP/UX production anyway, where we have absolutely no shared memory problems. So, my take on Linux (at least RH 7.1) is that it is a wonderful networking and firewall system, good development enivonment, but not so hot for shared memory hog databases (like DB2, Oracle, and Sybase). Perhaps PostGreSQL is written differently? Glen Austin
Post #19,491 by pwhysall 11/27/01 3:09:29 AM Reply	Re: Shared Memory Woes [link\|http://www-4.ibm.com/software/data/db2/extenders/netsearch/about.html\|http://www-4.ibm.co...h/about.html] "If your operating system has limits on shared resources, then use DB2 Text Information Extender as Net Search Extender has huge shared resource requirements with the need to store all data in main-memory. This may cause problems, although this depends on the size of your database and the available hardware." Stab in the dark, I know... Peter Shill For Hire [link\|http://www.kuro5hin.org\|There is no K5 Cabal]

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