Computers sometimes need more memory space than is available in RAM.  Virtual memory is a way to use disk space like memory.  Swap space is disk space on your SGI set aside to act as virtual memory space, should the need arise.  It is also used to boot a minimal OS for OS installations and to store a copy of the system memory during a crash.  IRIX allows two kinds of swap space and virtual swap space.  Raw swap space is a disk partition, usually partition 1 on your system drive.  You can also make a swap file on a filesystem, although this is slower than a swap partition.  Virtual swap space is available for programs that need it.

    Your SGI comes with a swap partition on the system drive.  This is usually enough space for most systems.  In some cases, such as with programs that reserve a lot of memory, it may be prudent to increase swap space.  Swap space is slower than real memory(RAM), and shouldn't be automatically used in place of a memory upgrade, unless no more RAM can be added.  In IRIX, the "swap" command lets the sysadmin manage swap space.  If you have a graphical system, you can also use the System Manager to manage swap space.  Repartitioning the system drive for more swap space is beyond the scope of this page, but I will give you the basic commands on swap space to get you started.

To list the current swap spaces:

swap -l

swap -a /dev/dsk/dks0d2s1

swap -d /dev/dsk/dks0d2s1

last updated 2/2800 by Martin McCormick, martinm@sas.upenn.edu