SGA Vs Physical Memory..
DBAsupport.com Forums - Powered by vBulletin
Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: SGA Vs Physical Memory..

  1. #1
    Join Date
    Feb 2003
    Posts
    69

    SGA Vs Physical Memory..

    Hi guys,

    I have little bit doubt can any one clear it off...

    How much % can i allocate to SGA from physical memory..

    Ex: H.D capacity is 40GB then how much % can allocate SGA ? is any default % for SGA ? and What is Fixed size ?
    HTML

  2. #2
    Join Date
    Dec 2002
    Location
    Bangalore ( India )
    Posts
    2,434
    Had you had a bit of knowledege about CO(Computer Organization) then You would have asked q like how much % of ( RAM size + Paging Mem ).

    Abhay.
    funky...

    "I Dont Want To Follow A Path, I would Rather Go Where There Is No Path And Leave A Trail."

    "Ego is the worst thing many have, try to overcome it & you will be the best, if not good, person on this earth"

  3. #3
    Join Date
    Dec 2001
    Location
    SAN FRANCISCO, CA
    Posts
    306
    yous should keep the GSA 60% or less of your physical ram
    Eat , Drink & Enjoy life -

    pravin_kini@hotmail.com

  4. #4
    Join Date
    Dec 2000
    Location
    Mumbai
    Posts
    38
    Hi

    1. Check out the total amount of physical memory (RAM) present on the database server.

    2. Check the total size of the database.

    3. Oracle recomends 1/3rd the size of the RAM, but it depends on the application and the type of transaction that will happen on the database.

    Better sit with Application Developers and the Account Manager, Know the system well then set the SGA size.

  5. #5
    Join Date
    Nov 2000
    Location
    greenwich.ct.us
    Posts
    9,092
    Originally posted by pravin
    yous should keep the GSA 60% or less of your physical ram
    Poppycock. On a box with 16G you want to leave 6.5G free? Oracle should use as much memory is on the box that prevents the box from swapping.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  6. #6
    Join Date
    Dec 2000
    Location
    Mumbai
    Posts
    38
    Dear Jeff

    SGA size should be defined by the DBA. It is not dynamically allocated by the Operating System. Swapping is done by operating system and will taken care will installation of operation system or you can add more swap space according to requirement. Dont mix with swapping and SGA.

  7. #7
    Join Date
    Nov 2000
    Location
    greenwich.ct.us
    Posts
    9,092
    Originally posted by shashikumar
    SGA size should be defined by the DBA. It is not dynamically allocated by the Operating System.

    Really?!?!?!

    Swapping is done by operating system and will taken care will installation of operation system or you can add more swap space according to requirement. Dont mix with swapping and SGA.
    Oil & Water. Drinking & Driving. Fertilizer & Diesel Fuel. Those are things that shouldn't be mixed.

    However, SGA and swapping are something that should be mixed. In fact, managing memory is a fundemental concept for operating a database.

    SGA > RAM == swapping
    SGA + User Sessions > RAM == swapping
    SGA + User Sessions + Box services > RAM == swapping
    SGA + User Sessions + Box services < RAM == good
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  8. #8
    Join Date
    Dec 2000
    Location
    Mumbai
    Posts
    38
    Well something is still not convinced.

    While designing SGA,

    1. Calculate the total no. of user sessions.
    2. Calculate apprx PGA size and the sort area size.
    3. Set the parameters for the SGA, depending on the database objects for sizing shared pool, log buffer or data buffer cache.

    When does the swapping occurs.. ?
    When there is no free space for user sessions in the database to perform their sort operations, then paging and swapping occurs.

  9. #9
    Join Date
    Nov 2000
    Location
    greenwich.ct.us
    Posts
    9,092
    Originally posted by shashikumar
    When there is no free space for user sessions in the database to perform their sort operations, then paging and swapping occurs.
    I think you are confusing sorting to swapping. Sorting occurs inside the database, swapping occurs outside the database in the OS. If oracle requests a page of memory that is not available the OS will swap some inactive memory to disk and then reuse it. When the inactive page of memory is needed again, it will be swapped back in and another page will be swapped out. Since Disk I/O is much slower than memory access, this will significantly slow down your database.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  10. #10
    Join Date
    Dec 2000
    Location
    Mumbai
    Posts
    38
    True....

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  



Click Here to Expand Forum to Full Width