RE: Suse 11 shmmax setting 11.2 install

Setting shmmax (the maximum size of an individual shared memory segment) to a very high number is harmless. Probably someone just set this value to the theoretical max (for a 64-bit system), without really thinking about it.

How much memory does the box have? It would be reasonable to set it to the total memory on the box, or, 1/2 the total memory on the box. Consider also, that if it's set too low, it usually won't cause a problem, unless it's set REALLY low.

If, for example, you set it to 1GB, and you create a DB with 10GB SGA, that just means you'll see 10 1GB shared memory segments, rather than one 10GB shared memory segment.

In general, set it to at least the size of the largest SGA of the database instances you'll be running on the server.

Note that in terms of absolute limit, SHMALL (which is measured in 4k pages) is more important. It's the total amount of memory on the box that can be allocated as shared memory.

Finally, while we're on the subject of memory, you didn't give any indication of how much memory is on this box, or how much you'll be allocating to shared memory, but, you should definitely look into using hugepages, unless the databases involved are very small.

Hope that helps,

-Mark

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Peter Hitchman Sent: Friday, August 05, 2011 3:19 PM
To: oracle-l
Subject: Suse 11 shmmax setting 11.2 install

Hi,
Looking for some advice here on installing into a 64 bit Suse environment:

SUSE Linux Enterprise Server 11 (x86_64) VERSION = 11
PATCHLEVEL = 1 Oracle EE 11.2

I have been stuck not being able to run the GUI installer because the machine is so remote from me, it never displays back to my X server, so I started going through the pre-reqs using cluvfy to help, when I came across the fact that shmmax is set to 18446744073709551615.

Now I am used to not changing a configuration if the setting is greater than Oracle needs, but cluvfy objects to this setting and I was taken aback by a value that is (2^64)-1.

I am trying to get all of the pre-reqs I can sorted so that I get an easier ride when I try to use the installer with a response file in silent mode.

What experience do others on the list have, who have used Suse, with this setting of shmmax , have you always changed it or left it as is?

Thanks

Pete
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http://www.freelists.org/webpage/oracle-l Received on Sat Aug 06 2011 - 07:24:05 CDT