Paging Space Overview

A paging space is fixed disk storage for information that is resident in virtual memory, but is not currently being accessed. A paging space, also called a swap space, is a logical volume with the attribute type equal to paging. This type of logical volume is referred to as a paging-space logical volume, or simply paging space. When the amount of free real memory in the system is low, programs or data that have not been used recently are moved from real memory to paging space to release real memory for other activities.

The following articles provide more information about paging spaces:

• Managing Paging Spaces
• Understanding Paging Space Allocation Policies

The following procedures explain various ways of managing paging spaces:

• Adding and Activating a Paging Space
• Changing or Removing a Paging Space
• Resizing or Moving the hd6 Paging Space

The "Virtual Memory Manager (VMM) Overview" explains how virtual memory is related to paging space.

The default paging space size is determined during the system customization phase of AIX installation according to the following standards:

• Paging space can use no less than 16MB except for hd6 which can use no less than 32MB in AIX Version 4.2.1 and later
• Paging space can use no more than 20% of total disk space
• If real memory is less than 32MB, paging space is two times real memory
• If real memory is greater than or equal to 32MB, paging space is real memory plus 16MB

There is another type of paging space available that can be accessed through a device that uses an NFS server for paging-space storage. For an NFS client to access this paging space, the NFS server must have a file created and exported to that client. The file size represents the paging space size for the client.

The logical volume paging space is defined by making a new paging-space logical volume or by increasing the size of existing paging-space logical volumes. To increase the size of an NFS paging space, the file that resides on the server must be increased by the correct actions on the server.

The total space available to the system for paging is the sum of the sizes of all active paging-space logical volumes.