If an application attempts to access an area outside its space, it results in an abnormal end to processing.

The result was that crashes (known as abends, short for abnormal ends) were possible and would result in stopping the system.

An ABEND (also abnormal end or abend) is an abnormal termination of software, or a program crash.

The latter, Detector, trapped execution "abends" (abnormal ends) to the execution of an instruction, displayed the contents of applicable fields, and could be told to apply a fix to the offending field so program execution could continue.

If no page has been assigned, SVS causes an Abnormal End (ABEND) with the same ABEND code (0C4) that MVT would have used for a protection violation.

It was therefore possible for bugs in NLMs to overwrite the kernel's or other NLM's address space and ultimately crash the server - in the mainframe-derived Novell terminology, this was known as an ABEND or ABnormal END.