Re: Why Oracle creates two shared memory segments instead of one?

"Vsevolod Afanassiev" <vafanassiev_at_yahoo.com> wrote in message news:1193352285.026233.151260_at_q5g2000prf.googlegroups.com...
>I noticed that on some platforms Oracle always creates two shared
> memory
> segments instead of one, even when both segments are much smaller than
> the
> limit.
>
> For example, on this Tru64 box the limit is set to 2 GB:
>
> oracle > sysconfig -q ipc
> ipc:
> msg_max = 8192
> msg_mnb = 16384
> msg_mni = 64
> msg_tql = 40
> shm_max = 2147483640 <<<---- Limit set to 2 GB
> shm_min = 1
> shm_mni = 1024
>
> Still Oracle creates two segments: one 8 MB, second 900 MB
>
> oracle> ipcs -am
>
> Shared Memory:
> T ID KEY MODE OWNER GROUP CREATOR CGROUP
> NATTCH SEGSZ CPID LPID ATIME DTIME CTIME
> m 1024 0x1e34 --rw-rw-rw- root daemon root
> daemon 4 524288 3679586 4104730 11:32:05 11:32:04
> 21:14:45
> m 2 0 --rw-r----- oracle dba oracle
> dba 9 8388608 4090358 4115445 8:40:03 8:40:13
> 10:58:11
> m 3 0x1c6492d0 --rw-r----- oracle dba oracle
> dba 9 947912704 4090358 4115445 8:40:03 8:40:13
> 10:58:11
>

Is Tru64 a NUMA implementation ?
Is this 10g.

There is a NUMA optimizations that does this by default in 10g: check parameter _enable_numa_optimization.

-- 
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
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