Hi,

This is my first post.

Below is my system architect:

2.6.9-78.0.13.ELsmp #1 SMP Wed Jan 7 17:45:52 EST 2009 x86_64 x86_64 x86_64 GNU/Linux

We had an Oracle Database Server with 16G of RAM. We encountered performance issue, so we added additional 16G or RAM.

Please let me know how large can I set kernel.shmmax value to in the /etc/sysctl.conf file.

Oracle doc. suggested to set it to half of the physical memory. But I would like to know whether it can set to a larger value so that I can increase Oracle SGA_MAX_SIZE to boost my DB performance.

Thank you in advance for your advice.

princessshieh

http://www.idevelopment.info/data/Or.../LINUX_8.shtml

You should find that the above link, particularly Chapter 3, answers your question

If there's anything you don't understand after reviewing that section, feel free to ask for more detail.

Cheers!
Sasha

PS - Welcome to LinuxQuestions!

Hi Sasha,

Thanks for your reply.

The link provided herein did not answer my question.

Basically I like to know what value I can set shmmax given the fact that there are total of 32G physical memory on my system. I have two Oracle instances on that box. I allocated 15 G for one of the instances, but only 500M for the 2nd one. That leaves some physical memory unused, I guess.

Since I have total of 32G, I feel like that I should be able to allocate more SGA to my first instance. But I am not sure how much I can set it to? If I increase SGA, then, I should change shmmax kernel parameter as well, right.

Thanks,

Karin