nswapdev(5)                                                     nswapdev(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      nswapdev - maximum number of devices that can be enabled for swap

 VALUES    [Toc]    [Back]
    Default
      10 devices

    Allowed values    [Toc]    [Back]
      Minimum: 1 device

      Maximum: 25 devices

 DESCRIPTION    [Toc]    [Back]
      Swap devices are managed in a table for easier indexing in the kernel.
      nswapdev sets the kernel variable responsible for the upper limit on
      this table, and thus the upper limit to devices which can be used for
      swap.

    Who is Expected to Change This Tunable?
      Anyone.

    Restrictions on Changing    [Toc]    [Back]
      Changes to this tunable take effect at the next reboot.

    When Should the Value of This Tunable Be Raised?
      If another swap device is added to the system which would increase the
      number of devices above nswapdev, and swapon() returns [ENOENT] to the
      caller (see the swapon(2) manpage).

    What Are the Side Effects of Raising the Value?
      More devices can be added to the system, and the kernel will need a
      little more memory for the table.  A small performance side effect of
      the kernel having to scan more devices to check for a duplicate device
      during swapon is also true, but realistically negligible.

    When Should the Value of This Tunable Be Lowered?
      Only if you are sure the system will never go over a certain number of
      swap devices, and you wish to lower this tunable to save a small
      amount of kernel memory and kernel performance during swapon
      operations.

    What Are the Side Effects of Lowering the Value?
      No side effects other than the primary and presumably desired new
      limitation on the number of swap devices.

    What Other Tunable Values Should Be Changed at the Same Time?
      None.

 WARNINGS    [Toc]    [Back]
      All HP-UX kernel tunable parameters are release specific.  This
      parameter may be removed or have its meaning changed in future



 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 nswapdev(5)                                                     nswapdev(5)
                          Tunable Kernel Parameters



      releases of HP-UX.

      Installation of optional kernel software, from HP or other vendors,
      may cause changes to tunable parameter values.  After installation,
      some tunable parameters may no longer be at the default or recommended
      values.  For information about the effects of installation on tunable
      values, consult the documentation for the kernel software being
      installed. For information about optional kernel software that was
      factory installed on your system, see HP-UX Release Notes at
      http://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      nswapdev was developed by HP.


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004