AIX 5L Problem Determination - IBM Redbooks

Do not extend a paging space logical volume into multiple physical volumes. If a
paging space logical volume is spread over multiple physical volumes, you will
not be spreading paging activity across all the physical volumes. If you want to
allocate space for paging on a physical volume that does not already have a
paging space logical volume, create a new paging space logical volume on that
physical volume.
For best system performance, put paging space logical volumes on physical
volumes that are each attached to a different disk controller.
7.5.2 Determining if more paging space is needed
Allocating more paging space than necessary results in unused paging space
that is simply wasted disk space. If you allocate too little paging space, a variety
of negative symptoms may occur on your system. To determine how much
paging space is needed, use the following guidelines:
► Enlarge paging space if any of the following messages appear on the console
or in response to a command on any terminal:
INIT: Paging space is low
ksh: cannot fork no swap space
Not enough memory
Fork function failed
fork () system call failed
Unable to fork, too many processes
Fork failure - not enough memory available
Fork function not allowed. Not enough memory available.
Cannot fork: Not enough space
► Enlarge paging space if the %Used column of the lsps -s output is greater
than 80.
Use the iostat, vmstat, and lsps commands to determine if you need to make
changes regarding paging space logical volumes:
# iostat
# vmstat
# lsps
If you wish to remove a paging space from the system or reduce the size of a
paging space, this should be performed in two steps. The first step in either case
is to change the paging space so that it is no longer automatically used when the
system starts. This is done with the chps command. For example:
# chps -a n paging00
Chapter 7. LVM, file system, and disk problem determination 167