The power loss-controlled shutdown mechanism allows the system to shut down in an orderly fashion following a loss of utility power. The power loss-controlled shutdown mechanism is available only if you connected the system to an uninterruptible power supply.
If utility power is not restored within the time that is specified by the QUPSDLYTIM system value, the Licensed Internal Code signals each job to end at the next instruction boundary. Typically a job is at the next instruction boundary or will be shortly. However, some long running instructions, such as those that build access paths or create programs, may not complete in the time that is allowed. After a fixed internal time to reach an instruction boundary, the changed pages in main storage are written to auxiliary storage, the system shuts down abnormally, and then powers off.
Successfully completing a power loss controlled shutdown causes the next initial program load (IPL) of the system programs to be considered normal by the Licensed Internal Code, but not by the operating system. If the uninterruptible power supply batteries do not hold the system long enough for the power loss-controlled shutdown to complete, the next IPL will be abnormal from the Licensed Internal Code viewpoint.