User Guide

14 Server Memory Administration Guide
Server Memory Administration Guide
103-000147-001
August 30, 2001
Novell Confidential
Manual 99a38 July 17, 2001
Virtual Memory
NetWare also provides a virtual memory system that swaps little-used data to
disk, thereby freeing memory for more frequently used data. Applications that
run in protected address spaces use virtual memory, as does Java*. The
following illustration shows the amount memory the server can recognize and
what portions the virtual memory system uses.
Virtual memory provides more efficient use of memory and lessens the
likelihood that low memory conditions will cause problems with the server.
Server operating system modules do not use virtual memory, because their
execution cannot be interrupted except at certain locations in these modules.
A periodic aging process assesses available memory to see which data has
been used less recently than the rest. Data that has not been used for some time
can be moved from memory to disk, thereby freeing memory for other uses.
When the data on disk is needed again, it is moved back into available
memory. Because data is swapped in and out of the disk, the available memory
can be used for a larger amount of data than its actual physical capacity would
allow.
0GB
64GB
4GB
Memory the server
operating system
can recognize
Memory used only
by the virtual
memory system
Memory used by
the file system,
NLM programs,
and device
drivers and can
be shared with
the virtual
memory system