Trouble resizing sga in 10g
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  1. #1
    Join Date
    Sep 2010
    Posts
    3

    Trouble resizing sga in 10g

    I ran into a strange problem trying to increase the size of SGA on my database.

    I have a system running 32 bit RHEL4 Enterprise edition. The machine has 8 GB of physical memory on it. The memory settings at the OS level are as follows (output of "ipcs -lm"):

    ------ Shared Memory Limits --------
    max number of segments = 4096
    max seg size (kbytes) = 4194303
    max total shared memory (kbytes) = 13118188
    min seg size (bytes) = 1

    I tried to modify the "sga_max_size" parameter to resize the SGA.

    There are 2 10g databases, 2 different versions (10.1.4 and 10.2.0) running on this machine. I tried to increase the memory setting for the 10.2.0 from 2gb to 3gb and it failed with the following error:

    ORA-27102: out of memory
    Linux Error: 12: Cannot allocate memory
    Additional information: 1
    Additional information: 851974

    On the 10.1.4 instance, when I tried to increase the memory from 1 gb to 2gb I got a similar error.

    What am doing wrong?

    Please advice.

    Thanks in advance.

  2. #2
    Join Date
    Mar 2007
    Location
    Ft. Lauderdale, FL
    Posts
    3,554
    I would say it is time to contact your Linux SA, in the mean time please do...
    cat /proc/sys/kernel/shmall
    getconf PAGE_SIZE

    Then do ((/proc/sys/kernel/shmall) * (PAGE_SIZE))/1024/1024/1024

    Resulting value is Gig of memory you can allocate as O/S level.

    Last but not least, you may want to check this link... http://www.puschitz.com/TuningLinuxF...ryOptimization by Werner Puschitz
    Last edited by PAVB; 09-18-2010 at 06:47 PM. Reason: typo
    Pablo (Paul) Berzukov

    Author of Understanding Database Administration available at amazon and other bookstores.

    Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.

  3. #3
    Join Date
    Sep 2010
    Posts
    3
    Since I have root access to this box, I've got the values:

    /proc/sys/kernel/shmall = 3279547
    PAGE_SIZE = 4096

    So based on the formula I should be able to access 12GB:
    (3279547 * 4096) / 1024/1024/1024 = 12 GB

    I'll read the link you sent and see if there is anything that I'm missing.

    Thanks
    Randy

  4. #4
    Join Date
    Sep 2010
    Posts
    3

    update

    I found that I can push my sga upto 1632M. Talking to a few of my friends, I was told that there is a patch for 10.1 that might help me take the system past the current limit.

    Thanks
    Randy

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