System Management Guide:
Operating System and Devices

Paging Space Configuration Tasks

This section provides instructions for the following paging space configuration tasks:

• Adding and Activating Paging Space
• Configuring Paging Space to Improve Performance

Adding and Activating Paging Space

To make paging space available to your system, you must add and activate the paging space. The total amount of paging space is often determined by trial and error. One commonly used guideline is to double the RAM size and use that figure as a paging space target. To use the Web-based System Manager wizard to increase paging space, select the Volumes container, then the Paging Space container. From the Selected menu, choose Increase Paging Space-> Wizard.

If you prefer to use SMIT, type one of the following fast paths on the command line:

• To list your current paging space, type: smit lsps
• To add paging space, type: smit mkps
• To activate paging space, type: smit swapon

Configuring Paging Space to Improve Performance

To improve paging performance, use multiple paging spaces and locate them on separate physical volumes whenever possible. However, more than one paging space can be located on the same physical volume. Although you can use multiple physical volumes, it is a good idea to select only those disks within the rootvg volume group unless you are thoroughly familiar with your system.

Setting the PSALLOC Environment Variable for Early Allocation Mode

The operating system uses the PSALLOC environment variable to determine the mechanism used for memory and paging space allocation. The default setting is late. For a description of the early and late alternatives for the PSALLOC environment variable, see Comparing Late and Early Paging Space Allocation in AIX 5L Version 5.2 System Management Concepts: Operating System and Devices.

The following examples show different ways to change the PSALLOC environment variable to early. The method you choose depends on how broadly you want to apply the change.

• Type the following command on a shell command line:

  PSALLOC=early;export PSALLOC

  This command causes all subsequent commands run from that shell session to run in early allocation mode.

• Add the following command in a shell resource file (.shrc or .kshrc):

  PSALLOC=early;export PSALLOC

  This entry causes all processes in your login session, with the exception of the login shell, to run under early allocation mode. This method also protects the processes from the SIGKILL signal mechanism.

• With root authority, add the following entry to the /etc/environment file:

  PSALLOC=early

  This entry causes all processes in the system, except the init process (process ID 1) to run in the early allocation mode. This method also protects the processes from the SIGKILL signal mechanism.

• Insert the putenv subroutine inside a program to set the PSALLOC environment variable to early. Using this method, the early allocation behavior takes effect at the next call to the exec subroutine.