Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> c.d.o.server -> Re: Why Oracle creates two shared memory segments instead of one?

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

From: <fitzjarrell_at_cox.net>
Date: Sat, 27 Oct 2007 08:10:56 -0700
Message-ID: <1193497856.691305.33440@d55g2000hsg.googlegroups.com>


Comments embedded.
On Oct 26, 2:35 pm, "Jonathan Lewis" <jonat..._at_jlcomp.demon.co.uk> wrote:
> "Vsevolod Afanassiev" <vafanass..._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 ?

It is, at least for newer releases:
http://h30097.www3.hp.com/informationlibrary.html

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

I expect this is the answer the OP was looking for. Good eye, Jonathan.

> --
> Regards
>
> Jonathan Lewishttp://jonathanlewis.wordpress.com
>
> Author: Cost Based Oracle: Fundamentalshttp://www.jlcomp.demon.co.uk/cbo_book/ind_book.html
>
> The Co-operative Oracle Users' FAQhttp://www.jlcomp.demon.co.uk/faq/ind_faq.html- Hide quoted text -
>
> - Show quoted text -

David Fitzjarrell Received on Sat Oct 27 2007 - 10:10:56 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US