Abend of a task or address space

The abend of a task or address space can be detected at the system, hardware, or application level.

System-detected problems

The system abnormally ends a task or address space when the system determines that the task or address space cannot continue processing and produce valid results.

For example, a task may incorrectly specify a request for a system service. Because the system cannot perform the service with incorrect input, the system abnormally ends the task requesting the service. This task is also referred to as a caller.

Hardware-detected problems

The system also abnormally ends a task with a completion code when the system receives control after a hardware-generated interruption that indicates an error in the task.

For example, an instruction in an application running in storage key 7 branches to low central storage, which is always in storage key 0. The difference in storage key causes a protection exception. The system recovers from this hardware problem by ending the application's task with an abend X'0C1'. If the application has a recovery routine, the system gives control to the routine; the routine can clean up resources being used by the application and can request a dump.

Application-detected problems

An application program abnormally ends itself when it determines that it cannot continue processing and produce valid results.

For example, an application may be calculating a total by successive additions. After each addition, the application checks the new total against a limit. If the total exceeds the limit, the application issues an ABEND macro to end abnormally and, perhaps, to ask for an ABEND dump. The ABEND macro specifies a user completion code.