topic Shared memory problem in Operating System - HP-UX

Shared memory problem

Gordon_3 — Fri, 27 Sep 2002 01:07:25 GMT

HI all,

I have encounter some issues about the shared memory usage, as u seen, below mainly have 3 apps running which require shared memory, Oracle, Sybase, and one called Datastage ( dsadm id ). I hit the problem of , if Sybase startup before Datastage, then Datastage will fail to startup, but if I reverse the sequence , both can start. Knowing that it's due to contigueous shared memory requirement, right? I just wanna will increase the shmax can ease this situation? Our config is quite large I think, total physical is 8G with now shmax is 3G....

Gordon

hkgdev2:/#ipcs -m
IPC status from /dev/kmem as of Fri Sep 27 09:59:00 2002
T ID KEY MODE OWNER GROUP
Shared Memory:
m 0 0x411c17c1 --rw-rw-rw- root root
m 1 0x4e0c0002 --rw-rw-rw- root root
m 2 0x41201f8d --rw-rw-rw- root root
m 18435 0x0c6629c9 --rw-r----- root sys
m 4 0x06347849 --rw-rw-rw- root root
m 1029 0xffffffff --rw-r--rw- root root
m 18438 0xdaec9611 --rw-rw-rw- root dstage
m 99335 0x6e3807e6 --rw------- sybase sybase
m 1032 0x6e380007 --rw------- sybase sybase
m 3081 0x6e38036f --rw------- sybase sybase
m 10 0xd502b578 --rw-r----- oracle oinstall
m 11 0xb0ed6e7c --rw-r----- root sys
m 15372 0x6e38037c --rw------- sybase sybase
m 248845 0xdaebd3bb --rw------- dsadm dstage
m 242702 0x6e380386 --rw------- sybase sybase
m 70672 0x00000000 --rw------- sybase sybase

Re: Shared memory problem

John Poff — Fri, 27 Sep 2002 01:16:04 GMT

Hi Gordon,

Are you running 32-bit apps? What version of HP-UX are you running?

There are some things you can do. Here are a couple of threads discussing shared memory. The first one deals with the contiguous problem, which sounds like what you are running into.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x5825543254bfd611abdb0090277a778c,00.html

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x1382107d277ad611abdb0090277a778c,00.html

JP

Re: Shared memory problem

Gordon_3 — Fri, 27 Sep 2002 01:34:57 GMT

HI John,

Thx for yr info, however, all the OS, Sybase, Datastage is runnning 64bit, so will it be other case else? Also can increase shmax ease this situation?

Gordon

Re: Shared memory problem

Ravi_8 — Fri, 27 Sep 2002 06:03:54 GMT

Hi Gordon

Apart from increasing shmmax consider increasing shmseg also, which increases the segment size of shared memory

Re: Shared memory problem

Gordon_3 — Fri, 27 Sep 2002 06:11:09 GMT

Hi Ravi,

My current shmseg setting is 512, is it too small?

Gordon

Re: Shared memory problem

Ravi_8 — Fri, 27 Sep 2002 06:21:52 GMT

Hi,

In one of my server running 2 oracle instances and a sybase instance shared memory values are as set below, running very well.

# kmtune|grep shm
shmem 1
shmmax 4294967295
shmmni 1024
shmseg 1024

Re: Shared memory problem

Ravi_8 — Fri, 27 Sep 2002 06:34:06 GMT

Hi (again)

ofcourse the memory is only 1GB

Re: Shared memory problem

Gordon_3 — Fri, 27 Sep 2002 06:35:32 GMT

Hi Ravi,

Not quite understand, u mean u have just 1G physical but can set to 4G shared mem??

Gordon

Re: Shared memory problem

Ravi_8 — Fri, 27 Sep 2002 06:42:25 GMT

Hi, Gordan

here is the info about the system which is running oracle9i and sybase.

# dmesg|grep -i phy
physical page size = 4096 bytes, logical page size = 4096 bytes
Physical: 1048576 Kbytes, lockable: 705268 Kbytes, available: 820344 Kbytes
# kmtune|grep shm
shmem 1
shmmax 4294967295
shmmni 1024
shmseg 1024

Re: Shared memory problem

Gordon_3 — Fri, 27 Sep 2002 06:44:27 GMT

Cool Ravi, this is the first time I know that shmax can set much higher than real physical, thx for info.