topic Re: Memory problems on HP-UX 11i in Operating System - HP-UX

Memory problems on HP-UX 11i

Rems Grinsteinss — Thu, 11 Jul 2002 09:51:16 GMT

Hi,
I am a Oracle DBA from Latvia.
My server configuration is HP 9000 L1000, 1 CPU, 256 RAM.

I have a performance problem. When server is recently booted everytiging works fine, but after a while it starts to work realy slow. It is my quess, that somehow memory is filled and not freed. Therefor Oracle uses swap instead of RAM. Also I have seen errors like "fork failed with status 12" and "bus error".

Can anyone suggest me something?

I have no performance tools installed on this server.

Re: Memory problems on HP-UX 11i

T G Manikandan — Thu, 11 Jul 2002 10:24:13 GMT

fork failed is that the user login or the system is unable to spawn new processes as the upper limit of the processes was reached.

check for values of the kernel parameters

maxuprc and nproc whether they are optimum for the server and user

maxuprc-->maximum number of user processes

nproc--->maximum total number of processes.

check for the /var/adm/syslog/syslog.log file for the bus error additional information.

Also post your kernel parameter values

Re: Memory problems on HP-UX 11i

James R. Ferguson — Thu, 11 Jul 2002 10:24:57 GMT

Hi:

You *really* need to add more memory. 256MB is pitifully small.

Errno 12 is an out-of-memory. You may be able to improve things slightly by adding more swap.

Check your swap utilization with:

# swapinfo -tam

Remember that you can add secondary device swap without a reboot, assuming thatyourkernel's 'maxswapchunks' doesn't need increasing. Choose swap device locations that are *not* on vg00 (with your primary one) and assign an equal swap priority to the secondary devices to arm I/O interleaving.

Regards!

...JRF...

Re: Memory problems on HP-UX 11i

harry d brown jr — Thu, 11 Jul 2002 10:24:58 GMT

If you haven't already, you can install a trial version of glance - which I think is good for 30 day's.

256MB of ram really isn't sufficient for oracle.

What version of 11 are you running, and what version of oracle?

Can you post your output from "kmtune" and "swapinfo"?

live free or die
harry

Re: Memory problems on HP-UX 11i

Sebastian Galeski_1 — Thu, 11 Jul 2002 10:25:44 GMT

Hi
as You wrote Your machine has not to much memory which for Oracle is critical.
If Yoy don't have any performance tool you always can use sar, top, iostat, vmstat to look where the bootleneck is.
So first of all use this tool and You will have a bit of information which allow You to investigate what is wrong.

What about kernel parameters were they prepared for data base server??? What about Oracle parameter did You set it right for your hardware??
regards seba

Re: Memory problems on HP-UX 11i

harry d brown jr — Thu, 11 Jul 2002 10:26:03 GMT

What application is receiving a "bus error" ??

live free or die
harry

Re: Memory problems on HP-UX 11i

T G Manikandan — Thu, 11 Jul 2002 10:38:05 GMT

sorry for the previous post

Error 12 is not enough space to spawn processes.

you can try adding additional swap.
Also you can enable swapmem_on on your kernel.

What are the values of

dbc_max_pct
dbc_min_pct
values

Thanks

Re: Memory problems on HP-UX 11i

Rems Grinsteinss — Thu, 11 Jul 2002 11:27:54 GMT

Thanks for all your answers. They gave me a lot of ideas.
I will add swap space.

But how to determine, which processes are using RAM and whitch Swap space?

If all Oracle database processes (ckpt, dbw, lgwr, smon, pmon) are using Swap space, can I still expect normal performance?

Where can I download Glance trial?

Re: Memory problems on HP-UX 11i

James R. Ferguson — Thu, 11 Jul 2002 11:36:55 GMT

Hi (again):

You can get a trial (30-day) version of Glance from the Application CDROM set. I believe that it's on the first CD.

Regards!

...JRF...

Re: Memory problems on HP-UX 11i

Bill Hassell — Thu, 11 Jul 2002 11:52:07 GMT

Here is a simple way to sort porcesses by the amount of RAM used:

UNIX95= ps -e -o vsz,ruser,pid,args | sort -rn | more

HOWEVER, Oracle uses a lot of additional memory (called shared memory) that is not accounted for in each process (because it is shared by several processes). If you want to see paging (ie, swapping) rates, use vmstat and look at the po (page out) column. Numbers larger than 1 digit) indicate very high paging rate which means: not enough RAM.

Oracle can be configured to use massive amounts of RAM and HP-UX will accomodate this request by using the swap area. In other words, you are trading off speed for RAM. As mentioned, Oracle needs a lot of memory to work efficiently. Use 256 megs and you'll get response times in minutes. Use 2000 to 4000 megs of RAM and you'll get response times of just a few seconds.

Oracle is far too expensive to be crippled with small RAM. Do a search through the forums on Oracle and memory and you'll see a lot of valuable information. Also note that 32bit Oracle is severely limited in the amount of RAM it can use. The 64bit version of Oracle is much more suited for L1000 system. And if you add a lot of users, 1 CPU is also too small...you'll need 2-4 CPUs for good performance.

Re: Memory problems on HP-UX 11i

Anonymous — Fri, 12 Jul 2002 05:49:18 GMT

In case you want to know some more about swap, memory etc pp have a look at
/usr/shar/doc/mem_mgt.txt

(excellent reading for sleepless nights;-)

Re: Memory problems on HP-UX 11i

Hartmut Lang — Fri, 12 Jul 2002 06:17:57 GMT

We had temporary hangs on a B2000 workstation runing HPUX11i with 256 Mb RAM only.
HP support had problems to find out the reason. But finally it was clear that the machine was in "thrashing" phase, because it was low on free RAM. It needs to push many pages from RAM to swap to make space run a new process.

What did help was:
- set swapmem_on to 0 helped something, because it made more pages in RAM available to swap out
- decrease the dbc_max_pct that dynamic buffer cache does not fill to much RAM
- adding another 512 Mb RAM. No problems any more!

HP support told my, that 256 Mb is propably not enough for runing HPUX11i.

Hartmut