topic Re: Shared memory issues. in Operating System - HP-UX

Shared memory issues.

David Diaz — Thu, 31 Jul 2003 17:49:35 GMT

Hi all,
I'm trying to run 5 instances of Sybase on a V class server with 10 processors and 8Gb of memory. I also have allocated 12Gb of swap space. Whenever I try to run any combo of instances that exceed 2.5Gb of shared (to Sybase) memory I get a "kistartup: could not create shared memory" error.
I have set the chatr command for the dataserver binary and ran the mlock command as well. Here are some kernel parms as well;

maxdsiz 2063597568
maxfiles 2048
maxfiles_lim 2048
maxswapchunks 6036
maxuprc 100
maxvgs 20
nfile (36*(NPROC+16+MAXUSERS)/10+32+2*(NPTY+NSTRPTY+NSTRTEL))
nproc (20+10*MAXUSERS)
nstrpty 60
shmmax 7784628224
shmmni 512
shmseg 512
swapmem_on 0
unlockable_mem 1024

My question is: It seems that Sybase has a memory usage limit of 2.5Gb. Is there a way around this? Maybe by installing several dataserver instances or somehow fooling the RDBMS into 'thinking' it's only using 2.5 when in reality it's using more by adjusting the kernel parms?
I know its a long shot but I'm a little desperate here.

Thanks in advance for your help.

Re: Shared memory issues.

Michael Steele_2 — Thu, 31 Jul 2003 18:12:45 GMT

Are you 64 bit O/S? I know this is a 64 bit v class server but did a 32 bit O/S accidently get installed?

# getconf KERNEL_BITS

############################################

Launch STM and excercise you're memory.

############################################

You need a 64 bit application for the higher shared memory limits. Surely SYBASE has a 64bit version.

Re: Shared memory issues.

David Diaz — Thu, 31 Jul 2003 18:31:47 GMT

OS is 64 bit.
Sybase is 32 bit. In fact I have the last of the Mohicans (11.9.2). We're going to the 64 bit version (12.5) sometime last quarter 2003 or first quarter 2004.

Re: Shared memory issues.

James R. Ferguson — Thu, 31 Jul 2003 18:56:57 GMT

Hi David:

You are doing about as well as you can with a 32-bit application. You need to move t the 64-bit database to even begin to utilize the memory you have. When you do, remember that the 'maxdsiz_64bit', 'maxtsiz_64bit' and 'maxtsiz_64bit' parameters apply. The unsuffixed variants are for 32-bit programs.

Regards!

...JRF...

Re: Shared memory issues.

Steven E. Protter — Thu, 31 Jul 2003 19:25:59 GMT

Last time I did a performance review we were maxing out at 50 shared memory segments.

512 might be a little high.

Here is a potentially useful tuning doc.

http://www1.itrc.hp.com/service/cki/search.do?category=c0&docType=Security&docType=Patch&docType=EngineerNotes&docType=BugReports&docType=Hardware&docType=ReferenceMaterials&docType=ThirdParty&searchString=UPERFKBAN00000726&search.y=8&search.x=28&mode=id&admit=-682735245+1059683118940+28353475&searchCrit=allwords

Document id: UPERFKBAN00000726

SEP

Re: Shared memory issues.

doug mielke — Thu, 31 Jul 2003 19:27:03 GMT

Is Sybase's structure different than Oracle's SGA?
On our 32 bit versions, we're limited to about the same amount, but only per instance. New instance, new SGA, another chunk of shared mem.
I'm wondering if this is system wide shared memory limit, or something else, like individual user space...

Re: Shared memory issues.

Tim Adamson_1 — Thu, 31 Jul 2003 22:36:42 GMT

Hi,

Have you considered implementing each of the DB instances in a separate memory window?

It was introduced via a patch and requires a kernel parameter to be changed.

See /usr/share/doc/mem_wndws.txt for more info.

It may get you out of a jam.

Cheers!

Re: Shared memory issues.

Harrison M Leal — Fri, 01 Aug 2003 11:55:16 GMT

Hi David

I have this problem, when you use one aplication in 32 Bits, your shared memory have one limitation of 2.75 Gb. Read this white paper, I believe that this document anger to help you.

http://www.docs.hp.com/hpux/onlinedocs/os/memwn1_4.pdf

Harrison.

Re: Shared memory issues.

David Diaz — Fri, 01 Aug 2003 16:42:04 GMT

Thanks for all your help guys.
The Memory Windows information was exactly what I needed. Using them I was able to start all 5 instances of Sybase with the required memory usage.
Again, much gratitude is owed to all of you.

David.