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Managing system performance

Configuring your system for Large Physical Memory

To configure memory above 4GB do the following:

  1. Set the following boot parameter in /stand/boot to enable the detection of memory above 4GB and switch to PAE mode: 
       ENABLE_4GB_MEM=YES

    NOTE: You must be in PAE mode to use memory above 4GB. If you want to switch out of PAE mode, you must reboot with ENABLE_4GB_MEM disabled (either defined as ``NO'', or not defined).

    To effect this change permanently, edit the file /stand/boot and add this line. (You can also interrupt the boot process using the interactive Boot Command Processor (BCP) to set this parameter temporarily.)

  2. If you want to dedicate memory, set the tunable parameter DEDICATED_MEMORY to the amount of memory required for PSE SHM, DSHM, or FGA-SHM (in pages). You can set the parameter using the System Tuner or the idtune command.

  3. Execute idbuild to rebuild the system using the values just defined.

  4. Reboot the system.

For example, on a system with 3GB of memory, the following sequence configures 2GB worth of pages as dedicated memory (note that you do not have to define ENABLE_4GB_MEM in this case):

  1. Enter the following commands:

    idtune DEDICATED_MEMORY 524288
    /etc/conf/bin/idbuild
    shutdown

Or, on a system with 8GB of memory, the following sequence configures 6GB worth of pages as dedicated memory:

  1. Define ENABLE_4GB_MEM=Y in /stand/boot.

  2. Enter the following commands:

    idtune DEDICATED_MEMORY 1572864
    /etc/conf/bin/idbuild
    shutdown

NOTE: An alternative way to divide memory between ``dedicated'' and ``general purpose'' uses is to define the specific amount of memory to be reserved for general purpose use (rather than to define the specific amount of dedicated memory you want):

  1. Set the tunable DEDICATED_MEMORY to 16777216 (that is, 64GB, the maximum value it can be set to).

  2. Set the tunable GENERAL_MEMORY to the amount of memory you want to reserve for that purpose (up to 4GB).

This alternative works because the tunable parameter GENERAL_MEMORY overrides DEDICATED_MEMORY if they conflict. There is an advantage to using this method because GENERAL_MEMORY acts as a safety net of sorts, allowing the system to at least boot and operate with adequate general memory should a bank of memory fail (not be present).

Next topic: Configuring swap space for systems with Large Physical Memory
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© 2007 The SCO Group, Inc. All rights reserved.
SCO OpenServer Release 6.0.0 -- 05 June 2007