IPL types and modes for IBM AS/400

Jun 16, 2021   
mainframe 
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Introduction

IBM mainframes such as the IBM AS/400 and IBM iSeries use an Initial Program Load (IPL) when the machine is started. This procedure allows various maintenance operations, but also to load the operating system.

IPL control panel

The IPLs can be chosen from the control panel on the front of the machine with the different buttons:

The IPL can be selected using function 02 on the control panel. Once in this function, we use the arrows to choose the IPL mode. We can for example choose the IPL 02 B N F. When the chosen IPL is the correct one we press Enter (blue button) to validate. We can use the control panel function 01 to display the chosen IPL and check that value. The display of the IPLs on this screen consists of 4 values:

List of IPL modes

There is two types of IPL Modes :

IPL Mode Description
Manual When the mode is set to Manual (M), the system allows you to do all manual IPLs, such as an operator-attended IPL from disk, CD-ROM or tape. Manual mode also allows you to do some manual control functions, such as selecting an IPL type and mode or displaying the kind of IPL that the system is set to run. However, in manual mode, you cannot do a remote IPL, an IPL by date and time, or an IPL after a power failure. Note: You should set the mode to Manual only when it is necessary. This ensures that no one accidentally presses the Power pushbutton and causes the system to stop.
Normal The Normal mode allows you to turn the power on and then automatically start the system in any of the following ways: IPL remotely IPL by date and time IPL after a power failure Note: Your system should be in Normal mode most of the time.

Types of IPL

IPL Description
A M Performs a Manual IPL from the A side of the disk. This mode may be used when applying or removing Licensed Internal Code (LIC) PTFs. It can also be used to power off the system. Use this type and mode only under the direction of your support representative.
A N Performs a Normal IPL from the A side of the disk. This mode should only be used when B N does not work and you are told to do so by your support representative.
B M Performs a Manual IPL from the B side of the disk. This mode should only be used when an attended IPL must be performed or you need to power off the system. This type of IPL is used when you need to change the system date and time permanently.
B N Performs a normal IPL from the B side of the disk. This is the type and mode used most of the time. It is also the mode the system must be in if you want to do an unattended IPL.
C M Allows service representatives to perform a special IPL. This mode is for use only by service representatives. Never IPL in this type and mode.
C N Allows service representatives to perform a special IPL. This mode is for use only by service representatives. Never IPL in this type and mode.
D M Performs a manual IPL from either CD-ROM or tape. This mode is used to install Licensed Internal Code and the OS/400 operating system in attended mode. This is the most often used IPL type and mode for installation.
D N Performs a normal IPL from either CD-ROM or tape. This mode is used to install Licensed Internal Code and the OS/400 operating system in unattended mode.

References