shared memory question

[Andrea Rossi]

I cant't understand the exact meaning of shmmax value. e.g. (rh 2.1 + oracle 9i):
root>cat /proc/sys/kernel/shmmax
800000000

but oracle is allocating two segments, 630MB each!

ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
0xf903c9dc 0 root 600 189 1
0x00000000 229377 ora92 640 4194304 21
0x00000000 262146 ora92 640 637534208 21
0x0dd19744 294915 ora92 640 624951296 105

Is shmmax the maximum memory value for each single segment? or per process? or what?

general memory info:

[root@sorasi01 root]# cat /proc/meminfo
total: used: free: shared: buffers: cached:
Mem: 2636201984 2627878912 8323072 815308800 225214464 1487982592
Swap: 2147426304 49283072 2098143232
MemTotal: 2574416 kB
MemFree: 8128 kB
MemShared: 796200 kB
Buffers: 219936 kB
Cached: 1405424 kB
SwapCached: 47684 kB
Active: 1590528 kB
Inact_dirty: 618036 kB
Inact_clean: 260680 kB
Inact_target: 643516 kB
HighTotal: 1703912 kB
HighFree: 5164 kB
LowTotal: 870504 kB
LowFree: 2964 kB
SwapTotal: 2097096 kB
SwapFree: 2048968 kB
BigPagesFree: 0 kB

[Jerome Henry]

HI,

It's the max shared memory for each segment.
have a read here for some more details and related infos :
http://www.puschitz.com/TuningLinuxForOracle.shtml#SettingSharedMemory

Hope it helps

Jerome Henry

[Andrea Rossi]

thanks a lot, useful.