Each Arbortext PE Unterprozess has a flag which is set any time it returns a fatal error. When a work thread detects an unusable Arbortext PE Unterprozess, it sets a flag that records the state of the Arbortext PE Unterprozess. At a later time, the work thread scans all running Arbortext PE Unterprozesse and requests the operating system to terminate any with the hung or fatal flag set to true.