FAQ
I have a two-node Oracle RAC 11.2.0.2 environment running multiple
databases on M3000 servers. Both servers are identical in configuration
with the exception that server A has twice the amount of physical memory
than server B (64GB versus 32GB). The following parameters are NOT set
in the SPFILE and therefore, DISM should not be enabled:



SGA_TARGET

SGA_MAX_SIZE

MEMORY_MAX_TARGET

MEMORY_TARGET



However, when I run the "ps" command at the OS, I observe the following:



Node A:

ps -ef|grep svt2d1|grep dism

root 13751 1 0 21:42:51 ? 0:00 ora_dism_svt2d101

root 13762 1 0 21:42:53 ? 0:00 ora_dism_svt2d101

root 13740 1 0 21:42:38 ? 0:00 ora_dism_svt2d101

root 13745 1 0 21:42:49 ? 0:00 ora_dism_svt2d101



Node B:

ps -ef|grep svt2d1|grep dism

root 7517 1 0 21:42:33 ? 0:00 ora_dism_svt2d102

root 7523 1 0 21:42:42 ? 0:00 ora_dism_svt2d102



So, node A has twice the number of DISM processes running than node B.
Based on my past experience with DISM with the previous Oracle database
versions, I have seen only one DISM process running per instance and
even in those situations, if the INIT parameters that impact DISM are
turned off, no DISM process was found running.





In the above RAC environment, when I run the "pmap" command, I see that
the shared memory segment is using ISM as shown below:

ps -ef|grep svt2d|grep pmon

oracle 13653 1 0 21:42:08 ? 0:13 ora_pmon_svt2d101



pmap -xs 13653 | grep ism

0000000380000000 1261568 1261568 - 1261568 4M rwxsR
[ ism shmid=0x7b00005f ]

00000003CD000000 8 8 - 8 8K rwxsR
[ ism shmid=0x7b00005f ]



So, based on the "pmap" command, it seems that DISM is turned OFF.



To conclude, the following was observed in a two-node 11.2.0.2 RAC
running on Solaris 10:

With the database INIT parameters that enable DISM not set, DISM
processes were found running on the server.

There were more than one DISM processes running for each
instance.

Server with twice the amount of RAM had spawned twice the number
of DISM processes than the one with half the amount of RAM.

The "pmap" command showed that the instance was actually using
ISM.

Has anyone made similar observations related to DISM in 11.2.0.2?



Thanks

Amir

Search Discussions

  • David Robillard at Jul 20, 2011 at 1:38 pm
    Hello Amir,
    Date: Tue, 19 Jul 2011 09:59:03 -0400

    I have a two-node Oracle RAC 11.2.0.2 environment running multiple
    databases on M3000 servers. Both servers are identical in configuration
    with the exception that server A has twice the amount of physical memory
    than server B (64GB versus 32GB). The following parameters are NOT set
    in the SPFILE and therefore, DISM should not be enabled:

    SGA_TARGET
    SGA_MAX_SIZE
    MEMORY_MAX_TARGET
    MEMORY_TARGET
    However, when I run the "ps" command at the OS, I observe the following:
    Take a look at appendix D « Administering Oracle Database on Solaris »
    in the « Oracle Database Administrator's Reference 11g Release 2
    (11.2) for Linux and UNIX-Based Operating Systems ». It's stated how
    and why Oracle uses Intimate Shared Memory on Solaris 10. (I'd give
    you the URL, but the documentation site appears to be down at the
    moment).

    If you "create pfile=''/tmp/pfile.txt'' from spfile;" can you see if
    the above parameters are set? If so, that might explain things.

    HTH,

    David
  • Hameed, Amir at Jul 20, 2011 at 2:31 pm
    David,
    Thank you for the feedback.
    I have already validated all DISM related parameters from SQL*Plus as
    well as by creating PFILE from SPFILE and none of the below mentioned
    parameters are set. The Oracle analyst that I am working with has filed
    a BUG with development (BUG# 12771380).

    Thanks
    Amir

    -----Original Message-----
    From: David Robillard
    Sent: Wednesday, July 20, 2011 9:38 AM
    To: Hameed, Amir
    Cc: oracle-l mailing list
    Subject: Re: DISM in 11.2.0.2 on Solaris 10

    Hello Amir,
    Date: Tue, 19 Jul 2011 09:59:03 -0400

    I have a two-node Oracle RAC 11.2.0.2 environment running multiple
    databases on M3000 servers. Both servers are identical in
    configuration
    with the exception that server A has twice the amount of physical memory
    than server B (64GB versus 32GB). The following parameters are NOT set
    in the SPFILE and therefore, DISM should not be enabled:

    SGA_TARGET
    SGA_MAX_SIZE
    MEMORY_MAX_TARGET
    MEMORY_TARGET
    However, when I run the "ps" command at the OS, I observe the
    following:

    Take a look at appendix D < Administering Oracle Database on Solaris >
    in the < Oracle Database Administrator's Reference 11g Release 2
    (11.2) for Linux and UNIX-Based Operating Systems >. It's stated how
    and why Oracle uses Intimate Shared Memory on Solaris 10. (I'd give
    you the URL, but the documentation site appears to be down at the
    moment).

    If you "create pfile=''/tmp/pfile.txt'' from spfile;" can you see if
    the above parameters are set? If so, that might explain things.

    HTH,

    David
  • Tanel Poder at Jul 20, 2011 at 6:02 pm
    Yep it could be a bug ... but if not, then my theory would be something like
    this:

    The oradism process gets started up even when you don't actually use DISM
    because it's also required for setting high priority processes (like VKTM &
    LMS processes - as specified by _high_priority_processes parameter). This is
    because you need root privs to raise the priority of a process and oradism
    (with root setuid) provides that.

    So perhaps that's the reason why the oradism process gets started despite
    you not using DISM.

    2) And now when the oradism gets started, why is there more than one process
    now - and why does it seem to be dependent on SGA size. This may be due to
    the fact that DISM memory is not locked to their physical memory locations
    by default. So, when extending/creating SGA, the dism process must call
    mlock() to lock these pages to RAM... and this mlock() call may likely have
    to walk through all the pages in the segment individually. Especially as
    DISM can fall back to small pages (when there's not enough contiguous large
    page frames available) then this locking activity may take a while (and burn
    kernel mode CPU). That would especially hurt you on the T-series CPUs where
    a single thread is dead slow. So, perhaps they've decided to parallelize
    this mlocking activity and it's not a bug at all.

    Let us know how it goes :-)

    --
    Tanel Poder
    http://blog.tanelpoder.com
    On Wed, Jul 20, 2011 at 5:31 PM, Hameed, Amir wrote:

    David,
    Thank you for the feedback.
    I have already validated all DISM related parameters from SQL*Plus as
    well as by creating PFILE from SPFILE and none of the below mentioned
    parameters are set. The Oracle analyst that I am working with has filed
    a BUG with development (BUG# 12771380).

    Thanks
    Amir

    -----Original Message-----
    From: David Robillard
    Sent: Wednesday, July 20, 2011 9:38 AM
    To: Hameed, Amir
    Cc: oracle-l mailing list
    Subject: Re: DISM in 11.2.0.2 on Solaris 10

    Hello Amir,
    Date: Tue, 19 Jul 2011 09:59:03 -0400

    I have a two-node Oracle RAC 11.2.0.2 environment running multiple
    databases on M3000 servers. Both servers are identical in
    configuration
    with the exception that server A has twice the amount of physical memory
    than server B (64GB versus 32GB). The following parameters are NOT set
    in the SPFILE and therefore, DISM should not be enabled:

    SGA_TARGET
    SGA_MAX_SIZE
    MEMORY_MAX_TARGET
    MEMORY_TARGET

    However, when I run the "ps" command at the OS, I observe the
    following:

    Take a look at appendix D < Administering Oracle Database on Solaris >
    in the < Oracle Database Administrator's Reference 11g Release 2
    (11.2) for Linux and UNIX-Based Operating Systems >. It's stated how
    and why Oracle uses Intimate Shared Memory on Solaris 10. (I'd give
    you the URL, but the documentation site appears to be down at the
    moment).

    If you "create pfile=''/tmp/pfile.txt'' from spfile;" can you see if
    the above parameters are set? If so, that might explain things.

    HTH,

    David
    --
    http://www.freelists.org/webpage/oracle-l

    --
    http://www.freelists.org/webpage/oracle-l

Related Discussions

Discussion Navigation
viewthread | post
Discussion Overview
grouporacle-l @
categoriesoracle
postedJul 19, '11 at 1:59p
activeJul 20, '11 at 6:02p
posts4
users3
websiteoracle.com

People

Translate

site design / logo © 2022 Grokbase