IPL considerations for uninterruptible power supply
When the system performs an initial program load (IPL), the Licensed Internal Code verifies various internal switches to see if the system was correctly turned off.
Only the successful completion of the Power Down System (PWRDWNSYS) command causes the system to be correctly turned off. For any other type of shutdown, the i5/OS® operating system considers the next IPL to be abnormal. The Licensed Internal Code considers the IPL to be normal if the system saves main storage and completes the power-down sequence successfully. If neither power-down technique completes normally, the Licensed Internal Code runs various recovery functions on the next IPL.
When an abnormal IPL occurs, the i5/OS program performs additional recovery functions. In an attended IPL, you can control some of these functions. In an unattended IPL that is caused by the Power restore IPL system value (QPWRRSTIPL) or a timed IPL, the system can only use the values that are currently set.
If the Power Down System (PWRDWNSYS) command is run while power is supplied by the battery backup unit or uninterruptible power supply, the system delays writing any job logs until the next IPL. The system handles this type of PWRDWNSYS so that the amount of processing is minimized. The system does not perform an IPL while operating on the battery backup unit.
You can perform an IPL on the system if utility power is off and the system is operating on an uninterruptible power supply. This does not apply to a timed or remote IPL. Only a manually initiated IPL is allowed when utility power is interrupted.
Parent topic:
Controlled shutdown conceptsRelated concepts
Power restore IPL system value (QPWRRSTIPL)Related reference
Uninterruptible power supply messages