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Swap, memory, kernal config? - ORA-12500 error

 
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TWBSupport
Regular Advisor

Swap, memory, kernal config? - ORA-12500 error

Hi All -
We have just went live on our new rp2470. Everything seemed fine, then users started getting the ORA-12500 error. Here's the history.. HPUX 11i running Oracle 9i. The application running on Oracle 9i is a 32 bit application & the only thing running on this system right now, the 11i is 64 bit. 2G RAM, SWAP was 4 G, I increased it to 8 G & that allowed approximately 50 more users get on. The server would start rejecting connections at about 127, then after the SWAP increase we got to about 178, but still receiving this error at 178. I need to allow 300 users on this system at once. Attached is my kmtune. Any advice would be greatly appreciated. Thank you!
36 REPLIES 36
Patrick Wallek
Honored Contributor

Re: Swap, memory, kernal config? - ORA-12500 error

Well, it sounds to me like if you increase your swap and more users get on then it is a memory issue.

2GB of RAM is WAY WAY too small for any server running Oracle. In my opinion that number should be 4GB or even more. The problem is that if your app is only 32-bit you will only use 3.75 GB of RAM. Oracle will be able to use more than 4GB of RAM since it is 64 bit, but that may cause problems with your app.

Steven E. Protter
Exalted Contributor
Solution

Re: Swap, memory, kernal config? - ORA-12500 error

I would look at shmmax

Very few kernel parameters have any effect on the number of possible oracle logins.

shmmax can be safely increased all the way up to 25% of memory. Memory is defined as memory plus swap.

As far as swap settings go, swap should be between 1.0 and 2.0 times physical memory. Anything higher and if you hit swap your machine will be as slow as can be.

Please post up swapinfo -tam

Before you increase swap, you should make sure you are using it.

I'm attaching a performance data collection script in case there are other bottlenecks triggering the problem.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
TWBSupport
Regular Advisor

Re: Swap, memory, kernal config? - ORA-12500 error

Patrick -
I guess when I read Oracles' recommendations for RAM, (512 for server, 512 for Mgmt) & then I doubled it. I thought we would be good to go...


Steven -
As always you have given me a great tool here. No problems jumped out at me, but I'll take a longer look at it in a few minutes. Here's the swapinfo you requested.
Patrick Wallek
Honored Contributor

Re: Swap, memory, kernal config? - ORA-12500 error

You are actually using some of your swap space which is not good. That could drastically slow down your machine. You also have 3772MB reserved and about 450 MB actually in swap, which is more than your 2GB of RAM. That totals up to more than 4GB.

I would definitely add RAM to this machine to start with. If HP RAM is too expensive for you, you could try Kingston, Crucial or DataRam. I have used Kingston in the past with no problem and they are MUCH MUCH MUCH cheaper than HP and they come with a lifetime warranty.
Steven E. Protter
Exalted Contributor

Re: Swap, memory, kernal config? - ORA-12500 error

I would add HP ram, especially if you have a support contract. It might not seem fair, but HP hardware support doesn't look favorably on a system that has non-HP memory in it. They tend to try and back away from the call.

Your application will perform better if its not swapping most of the time. Your ram to swap ratio is bad and your system is likely to slow down to a crawl when swap gets hit hard.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
TWBSupport
Regular Advisor

Re: Swap, memory, kernal config? - ORA-12500 error

Thank you both for your replies. I will order the HP RAM. Once I install the new RAM, do I just delete the extra SWAP space I created, by lvreducing?
Patrick Wallek
Honored Contributor

Re: Swap, memory, kernal config? - ORA-12500 error

No, you cannot delete a swap area without rebooting the machine.

If you want, you can leave the swap there "just in case". Also, depending on how much RAM you add, you will either need the extra swap or you will need to turn "swapmem_on" on (set it to 1) so you can actually use all of the RAM in your system.
Steven E. Protter
Exalted Contributor

Re: Swap, memory, kernal config? - ORA-12500 error

That depends on how much RAM you order.

If you add another 2 GB of ram, that will take you to 4GB.

You have two 4 GB swap areas totalling 8 GB.

That would leave you with a ram to swap ratio of 2.0 which would be reasonable.

You can make one swap area priority 1 and the second priority 2 so it doesn't get used so often.

A more optimal setup would be this:

RAM is now 4 GB

primary swap is 2 GB priority 1 or zero.
A secondary swap area of 4 GB set to priority 2.

This would lead to optimal peformance when hitting small amounts of swap.

If you are adding more than 2 GB of RAM than don't remove any sway area at all, just change the priority, maybe optimize as noted in my prior two paragraphs.

SEP
Steven E Protter
Owner of ISN Corporation
http://isnamerica.com
http://hpuxconsulting.com
Sponsor: http://hpux.ws
Twitter: http://twitter.com/hpuxlinux
Founder http://newdatacloud.com
TWBSupport
Regular Advisor

Re: Swap, memory, kernal config? - ORA-12500 error

Thanks a ton for the advice!