AIX 5L Problem Determination - IBM Redbooks

The memory columns
The memory columns provide information about the real and virtual memory.
Under memory for the vmstat command are two additional columns, avm and fre.
The avm column
The avm (Active Virtual Memory) column gives the average number of 4-KB
pages that are allocated to paging space. The avm value can be used to
calculate the amount of paging space assigned to executing processes.
Note: The vmstat command (avm column), ps command (SIZE, SZ), and
other utilities report the amount of virtual memory actually accessed, but with
delayed page space algorithm, the paging space may not get touched. The
svmon command (up through AIX Version 4.3.2) shows the amount of paging
space being used, so this value may be much smaller than the avm value of
the vmstat command.
For more information on DPSA, see the IBM ^ Certification
Study Guide - AIX 5L Performance and System Tuning, SG24-6184.
The number in the avm field divided by 256 will yield the approximate number of
megabytes (MB) allocated to the paging space system wide. Prior to AIX Version
4.3.2, the same information is reflected in the Percent Used column of the lsps
-s command output or with the svmon -G command under the page space inuse
field, pg.
The fre column
The fre column shows the average number of free memory pages. A page is a
4-KB area of real memory. The system maintains a buffer of memory pages,
called the free list, that will be readily accessible when the VMM needs space.
The minimum number of pages that the VMM keeps on the free list is determined
by the minfree parameter of the vmtune command. When an application
terminates, all of its working pages are immediately returned to the free list. Its
persistent pages (files), however, remain in RAM and are not added back to the
free list until they are stolen by the VMM for other programs. Persistent pages
are also freed if the corresponding file is deleted.
For this reason, the fre value may not indicate all the real memory that can be
readily available for use by processes. If a page frame is needed, then persistent
pages related to terminated applications are among the first to be handed over to
another program.
The page columns
The page columns show information about page faults and paging activity.
These are averaged over the interval and given in units per second.
248 IBM ^ Certification Study Guide - AIX 5L Problem Determination Tools and Techniques