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Memory problems on HP-UX 11i

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Rems Grinsteinss
Occasional Contributor

Memory problems on HP-UX 11i

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.
11 REPLIES
T G Manikandan
Honored Contributor

Re: Memory problems on HP-UX 11i

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

James R. Ferguson
Acclaimed Contributor

Re: Memory problems on HP-UX 11i

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...
harry d brown jr
Honored Contributor

Re: Memory problems on HP-UX 11i

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
Live Free or Die
Sebastian Galeski_1
Trusted Contributor

Re: Memory problems on HP-UX 11i

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
harry d brown jr
Honored Contributor

Re: Memory problems on HP-UX 11i


What application is receiving a "bus error" ??

live free or die
harry
Live Free or Die
T G Manikandan
Honored Contributor

Re: Memory problems on HP-UX 11i

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
Rems Grinsteinss
Occasional Contributor

Re: Memory problems on HP-UX 11i

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?
James R. Ferguson
Acclaimed Contributor

Re: Memory problems on HP-UX 11i

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...
Bill Hassell
Honored Contributor
Solution

Re: Memory problems on HP-UX 11i

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.


Bill Hassell, sysadmin
Anonymous_User1
N/A

Re: Memory problems on HP-UX 11i

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;-)
Hartmut Lang
Trusted Contributor

Re: Memory problems on HP-UX 11i

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