Publishing Engine Programmer's Guide > The Arbortext Publishing Engine Request Manager > Understanding the Internal Structure of Arbortext PE Request Manager > Arbortext PE sub-process Pool Management > Arbortext PE sub-process Pool Work Thread > Terminating Unusable Arbortext PE sub-processes
  
Terminating Unusable Arbortext PE sub-processes
Each Arbortext PE sub-process has a flag which is set any time it returns a fatal error. When a work thread detects an unusable Arbortext PE sub-process, it sets a flag that records the state of the Arbortext PE sub-process. At a later time, the work thread scans all running Arbortext PE sub-processes and requests the operating system to terminate any with the hung or fatal flag set to true.