PAGING SPACE

PAGING SPACE

Paging space is configured for additional system performance i.e. if real memory is occupies some system process, that time further process is moved to paging space temporary. If real memory getting free, then process moved from paging space to real memory. This paging space is assigned from HDD space.

Normally paging space is configured double size of the real memory

If system has 512MB RAM, then paging space size will be 1BG.

In this paging space we can do following things

1. List paging space
2. Create paging space
3. Change paging space
4. Activate paging space
5. Deactivate paging space
6. Remove paging space

1. List paging space

Using lsps command we can view the paging space details

#lsps –a (It will display the paging space details)

2. Create Paging space

Using mkps command we can create the paging space

#mkps –s 10 rootvg hdisk2

s- size

10 – no of PP size

Rootvg – specifying the VG

Hdisk2 – paging space created in PV hdisk2 (PP allocated from hdisk2)

Then paging space has created and name will be paging00

Using mklv command we can create paging space using different name.

Generally paging name will be paging00, paging01, paging02,

#mklv –y newpaging –t paging rootvg 10 hdisk2

#lsps –a

Paging00 , newpaging

 3. Change paging space

Using chps command we can increase, decrease, auto on, and auto off the paging space.

#chps –s 5 newpaging (5 LP’s added with newpaging) – To increase

#chps –d 3 newpaging (3 LP’s reduced from newpaging – To Decrease

#chps -ay newpaging (To start the paging space at startup)

#chps –an newpaging (To stop the paging space automatic startup at boot)

4. Activate paging space

Using swapon command we can activate the paging space

#swapon /dev/newpaging (To activate paging space)

The paging space is active stage, and then one entry will be available in /etc/swapspaces file.

5. Deactivate paging space

Using swapoff command we can deactivate the paging space

#swapon /dev/newpaging (To deactivate paging space)

The paging space is deactivated, then that paging space entry is removed from /etc/swapspaces

6. Remove paging space

Using rmps command we can remove the paging space

#rmps newpaging

NOTE:

Before removing the paging space, paging space should be offline, then we can remove the paging space, otherwise it will give some errors

Paging space concepts

A paging space is a type of logical volume with allocated disk space that stores information which is resident in virtual memory but is not currently being accessed.

This logical volume has an attribute type equal to paging, and is usually simply referred to as paging space or swap space. When the amount of free RAM in the system is low, programs or data that have not been used recently are moved from memory to paging space to release memory for other activities.

Another type of paging space is 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 amount of paging space required depends on the type of activities performed on the system. If paging space runs low, processes can be lost, and if paging space runs out, the system can panic. When a paging-space low condition is detected, define additional paging space.

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.

Paging space default size

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 16 MB, except for hd6 which can use no less than 64 MB in AIX 4.3 and later.

·         Paging space can use no more than 20% of total disk space.

·         If real memory is less than 256 MB, paging space is two times real memory.

·         If real memory is greater than or equal to 256 MB, paging space is 512 MB.

Paging space file, commands, and options

The /etc/swapspaces file specifies the paging spaces and the attributes of the paging spaces.

A paging space is added to the /etc/swapspaces file when it is created by the mkps command, and a paging space is removed from the/etc/swapspaces file when it is deleted by the rmps command. The paging space attributes in the file are modified by the chps -acommand or the chps -c command. This is a change from AIX® 5.3 and earlier, when only automatically swapped-on devices, as specified by the mkps -a command or the chps -acommand, were kept in the /etc/swapspaces file. Files using a previous format (where there are no attributes for checksum size and automatic swap-on in the stanzas) continue to be supported. If the paging space size is too large, you can subtract logical partitions from the paging space without rebooting using the chps -dcommand.

The paging type option is required for all logical volume paging spaces.

The following options are used to maximize paging performance with a logical volume:

·         Allocate in the middle of the disk to reduce disk arm travel

·         Use multiple paging spaces, each allocated from a separate physical volume.

Setting the paging space on an AIX system

For parallel jobs that process large amounts of data, your system must have the minimum settings for the paging space.

Attention: Only a system administrator with root privileges should reset the system paging space.

Procedure

To set the paging space on an AIX^® system:

1. Run the following command on each node or workstation in your system to determine the current paging size for a node or workstation.

node: $ lsps -a

The lsps command displays information in the form shown in this table.

Page Space	Physical Volume	Volume	Group Size	% Used	Active	Auto	Type
paging01	hdisk1	pagevg	2000MB	1	yes	yes	lv
paging00	hdisk0	rootvg	192MB	5	yes	yes	lv
hd6	hdisk0	rootvg	64MB	23	yes	yes	lv

The Group Size column lists the paging size for each disk drive. In this case, the total for the node is 2000 + 192 + 64 MB = 2256 MB (approximately 2.2 GB).

You can also run the following dsh command from the control workstation of an AIX RS/6000^® SP™ to display paging size information about all nodes: control: $ dsh -a lsps -a

2. Change the paging space as necessary for each node or workstation.

If you need more Paging space command, click the following link,

paging space