topic Re: Oracle/RedHat6.2 and Kernel Parameters in Operating System - Linux

Oracle/RedHat6.2 and Kernel Parameters

Dan Nixon — Thu, 15 Mar 2001 22:20:04 GMT

I want to install an Oracle database on a RedHat 6.2 installation. It appears to be a 6.2 Standard addition. I know there is a Redhat release 6.2E that appears to be specifically tuned for Oracle. I checked the kernel header files and they are not up to par with Oracle's recommendations. Is there kernel source for 6.2E that I can download from Redhat to the tuned kernel parameters.

If not, I will need to edit the appropriate header files. I have some questions regarding the format and some comments in the files.

#define SHMMAX 0x2000000 /* max shared seg size (bytes) */
/* Try not to change the default shipped SHMMAX - people rely on it */

For SHMMAX, can the comment be ignored and what format can the value be in?

Re: Oracle/RedHat6.2 and Kernel Parameters

Dieter Degrendele_1 — Mon, 19 Mar 2001 12:46:49 GMT

Hi,

The format for max shared memory is in hex, thus 0x... The parameter should be changed only if you work with really big databases.

Re: Oracle/RedHat6.2 and Kernel Parameters

Dapid Candra — Thu, 22 Mar 2001 04:12:13 GMT

I think you can change the kernel parameter on the fly (but require database restart to take effect).

issue this command as root:

echo 2147483647 > /proc/sys/kernel/shmmax

I use 2^31-1. I suggest you try several value until you get the largest value possible for your server.
Someone gave me larger value than that, but my server cannot accept it and I start divide the value by two. If the new value ca not be accepted, I divide it again by two, and so on.

You know if the value is accepted by issuing this command:

cat /proc/sys/kernel/shmmax

if the output is NOT -1 and similar with value you assigned, then the kernel accept the new value.

You should upgrade your kernel, if you can not not find /proc/sys/kernel/shmmax or you can not assign any value.

Make sure to add the command to rc.local (or elsewhere, depends on your server config), so that the changes always take effect when server restart and before database startup.

Re: Oracle/RedHat6.2 and Kernel Parameters

Dan Nixon — Thu, 22 Mar 2001 22:06:09 GMT

Dieter

I'm not familiar with this syntax for hex. How do you calcualte it.

-Dan

Re: Oracle/RedHat6.2 and Kernel Parameters

Steven Sim Kok Leong — Wed, 28 Mar 2001 06:13:43 GMT

Hi,

man ascii gives you the hexadecimal equivalent of decimals from 0 to 26 and also 127.

You can use the od command on your linux system to compute the hexadecimal equivalent of any decimals.

Alternatively, if you have a Windows PC, you can run "calc" to perform the translation between hexadecimal and decimal numbers.

Hope this helps. Regards.

Steven Sim Kok Leong
Brainbench MVP for Unix Admin
http://www.brainbench.com