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Allocation of memory to Oracle 11g instance

975148 Newbie
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We have a Vmware RHEL instance with 16GB of memory allocated to it. I had a query that is it possible to allocate 8GB from that for the Oracle database? My guess is no because Oracle database is automatically going to allocate the memory for itself but I may be wrong.

I hope, my question is clear that is it possible to allocate a certain amount for memory for the database.

Please revert with the reply to my query.

Regards
  • 1. Re: Allocation of memory to Oracle 11g instance
    Mihael Pro
    Currently Being Moderated
    972145 wrote:
    We have a Vmware RHEL instance with 16GB of memory allocated to it. I had a query that is it possible to allocate 8GB from that for the Oracle database? My guess is no because Oracle database is automatically going to allocate the memory for itself but I may be wrong.
    you limit memory for oracle instance by database parameters
    additional memory will be required for user sessions

    note that Oracle is not certified on vmware

    Edited by: Mihael on Jan 14, 2013 2:40 AM
  • 2. Re: Allocation of memory to Oracle 11g instance
    Rob_J Journeyer
    Currently Being Moderated
    Look up in the docs about SGA_TARGET, SGA_MAX_SIZE, MEMORY_TARGET and PGA_AGGREGATE_TARGET

    These are some of the parameters which can help you to size your Oracle database.
  • 3. Re: Allocation of memory to Oracle 11g instance
    BillyVerreynne Oracle ACE
    Currently Being Moderated
    972145 wrote:
    We have a Vmware RHEL instance with 16GB of memory allocated to it. I had a query that is it possible to allocate 8GB from that for the Oracle database?
    Yes. Set /dev/shm to 8GB to make 8GB of total shared memory available to the kernel to allocated (via the shm kernel interface used by Oracle).

    Then set the Oracle instance's set SGA_MAX_SIZE/SGA_TARGET to 8GB.

     
    PS. You may want to set +/dev/shm+ higher than 8GB as other processes and services also use the shm kernel interface for memory - allowing Oracle a full 8GB allocation.

    Edited by: Billy Verreynne on Jan 14, 2013 11:12 AM
  • 4. Re: Allocation of memory to Oracle 11g instance
    Bawer Journeyer
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    972145 wrote:
    I had a query that is it possible to allocate 8GB from that for the Oracle database?
    Yes, but It is probably easier for you to use the Enterprise Manager.
  • 5. Re: Allocation of memory to Oracle 11g instance
    BillyVerreynne Oracle ACE
    Currently Being Moderated
    Bawer wrote:
    972145 wrote:
    I had a query that is it possible to allocate 8GB from that for the Oracle database?
    Yes, but It is probably easier for you to use the Enterprise Manager.
    It does not changes +/dev/shm+ - which by kernel default is set to 50% of available RAM. Which means that on a 16GB RAM box, Enterprise Manager cannot make Oracle use more than 8GB. Unless +/dev/shm+ is changed first to a larger allocation.

    I also have a basic issue with your suggestion - dumbing down administration. Point-and-click on pretty button in shiny GUI to make a configuration change. With no knowledge about what that button does, what it changes, and how to change and maintain that without a GUI when a GUI is not available. Like in the middle of a night. Doing remote support. On a critical production server. Where only a console interface is available.

    A sysadmin or DBA that needs a GUI to make changes, is like a one legged man running a race using a crutch. GUI admin tools like Enterprise Manager are not intended to be used as a crutch for filling the void of knowledge that a sysadmin or DBA is expected to have.
  • 6. Re: Allocation of memory to Oracle 11g instance
    jgarry Guru
    Currently Being Moderated
    But the OP question was to make Oracle use 8G.
  • 7. Re: Allocation of memory to Oracle 11g instance
    Bawer Journeyer
    Currently Being Moderated
    Billy  Verreynne  wrote:

    I also have a basic issue with your suggestion - dumbing down administration...
    I didn't say that every dba needs EM to manage the instances ;-)

    but if op asks same kind of questions as above, I assume he is a newbie and doesn't have the enough knowledge about managing the instance or doing backup/recover using sqlplus/rman.
  • 8. Re: Allocation of memory to Oracle 11g instance
    975148 Newbie
    Currently Being Moderated
    Thanks for your answer but is it not true that SGA+PGA cannot be more than 1GB of allocation.
  • 9. Re: Allocation of memory to Oracle 11g instance
    Aman.... Oracle ACE
    Currently Being Moderated
    972145 wrote:
    Thanks for your answer but is it not true that SGA+PGA cannot be more than 1GB of allocation.
    Do you mean to say that SGA+PGA can't be more than 1gb? If yes, no, it's not true.

    Aman....
  • 10. Re: Allocation of memory to Oracle 11g instance
    BillyVerreynne Oracle ACE
    Currently Being Moderated
    Bawer wrote:
    Billy  Verreynne  wrote:

    I also have a basic issue with your suggestion - dumbing down administration...
    I didn't say that every dba needs EM to manage the instances ;-)

    but if op asks same kind of questions as above, I assume he is a newbie and doesn't have the enough knowledge about managing the instance or doing backup/recover using sqlplus/rman.
    I'll rather have a newbie going through the learning curve early. Than put it off and put it off using EM and other GUIs as crutches... and then becoming just like many Windows sysadmins I knew. Incapable of sysadmin when facing a complex problem, without mouse and GUI, only having the keyboard, knowledge and experience at hand. :-)
  • 11. Re: Allocation of memory to Oracle 11g instance
    BillyVerreynne Oracle ACE
    Currently Being Moderated
    jgarry wrote:
    But the OP question was to make Oracle use 8G.
    Yep, but if ASM is used for example, or X-Windows are running on the console, etc. - there will be less than the full 8G of shared memory available via the shm interface for the Oracle db instance to grab for the SGA.
  • 12. Re: Allocation of memory to Oracle 11g instance
    975148 Newbie
    Currently Being Moderated
    Thanks for your answer but when I did,

    df -h

    on the server, it has not shown /dev/shm.
  • 13. Re: Allocation of memory to Oracle 11g instance
    975148 Newbie
    Currently Being Moderated
    Request you if you can please update. Thanks.
  • 14. Re: Allocation of memory to Oracle 11g instance
    sb92075 Guru
    Currently Being Moderated
    972145 wrote:
    Thanks for your answer but when I did,

    df -h

    on the server, it has not shown /dev/shm.
    do NOT tell us what you think happened, SHOW us
    [oracle@localhost ~]$ df -h
    Filesystem            Size  Used Avail Use% Mounted on
    /dev/hda1              11G  2.3G  7.3G  25% /
    /dev/hdb1              12G  6.9G  4.2G  63% /home
    tmpfs                 444M  284M  160M  64% /dev/shm
    [oracle@localhost ~]$ 
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