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

-- 
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html


<fitzjarrell_at_cox.net> wrote in message 
news:1193497856.691305.33440_at_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
>