All,

Recently we've been working with some share memory problems and we've notice 
some strange numbers in the most current kernels of sles 10 sp2

on kernel 2.6.16.60-0.37_f594963d-default #1 SMP Mon Mar 23 13:39:48 UTC 2009

We see the following default settings:

r...@lnxfdts1:DCTEST1:~ # ipcs -l

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 3217741
max total shared memory (kbytes) = 8388608
min seg size (bytes) = 1

Which are expected, but on any later kernels-

2.6.16.60-0.39.3-default #1 SMP Mon May 11 11:46:34 UTC 2009
or
2.6.16.60-0.42.5-default #1 SMP Mon Aug 24 09:41:41 UTC 2009 (most current 
kernel for sles10sp2)

We see

r...@lnxmaint:DCTEST1:~ # ipcs -l

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 18014398509481983
max total shared memory (kbytes) = 4611686018427386880
min seg size (bytes) = 1


I don't know about you, but that total shared memory can't be good to have that 
large of a number.  Is this a bug (or a feature ;) )?

Also reading around I see that the max total shared memory should be equal to 
your actual memory and max seg size should be equal to 75-90% of your memory 
(depending on if you are reading from oracle or db2)

Any thoughts or comments that might shed some light on this?

Thanks in advance,

Deric Abel
zLinux Administrator
America First Credit Union

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