Can I increase the SHMMAX  (Shared Memory Max) value from 16GB to 64GB?

Posted on 2009-02-19
Last Modified: 2013-12-27
I wants to increase the value of SHMMAX from 16GB to 64GB as Oracle expert recommended. The expert recommended to increase it from existing 16GB to 64GB. Is there any side effect to the system? Can Solaris 8 accept?  

The server has 160GB of memory. And SHMMAX=Max Shared Memory Segment. If I use the recommendation from Oracle expert which is 64GB, 2 segments will use 128GB of memory. Is it possible to grab 128GB of memory on the fly. Since the server has 160GB of memory, he can at most grab 2 segments, provided there is enough memory.

----- Current value ----
* IPC Shared Memory
8589934592 max shared memory segment size (SHMMAX)
512 shared memory identifiers (SHMMNI)
Thanks in advance,
Question by:Dujin
    LVL 6

    Accepted Solution

    That depends on wich version of Solaris is used.
    Earlier versions could cause the OS to run out of memory/swap.
    In your case Solaris 8, I belive it has safeties built into to prevent that.

    In Solaris10, setting kernel parameters in /etc/system is an obsolete method. Solaris 10 has a Resource Manager which is used to adjust these kernel params.


    Author Closing Comment

    The website below is the correct document for me.
    As the document said "Setting this value high does not hurt anything, as this merely is a limit - nothing is pre-allocated.", increasing the SHMMAX value should be OK.

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    IT, Stop Being Called Into Every Meeting

    Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

    Note: this article covers simple compression. Oracle introduced in version 11g release 2 a new feature called Advanced Compression which is not covered here. General principle of Oracle compression Oracle compression is a way of reducing the d…
    Cursors in Oracle: A cursor is used to process individual rows returned by database system for a query. In oracle every SQL statement executed by the oracle server has a private area. This area contains information about the SQL statement and the…
    This video shows how to Export data from an Oracle database using the Datapump Export Utility.  The corresponding Datapump Import utility is also discussed and demonstrated.
    This video explains what a user managed backup is and shows how to take one, providing a couple of simple example scripts.

    779 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    14 Experts available now in Live!

    Get 1:1 Help Now