When a work thread terminates an Arbortext PE サブプロセス, the pool queues deletion of its temporary directory. Each pool maintains a list of deferred directory deletion requests. However, directory deletion is performed after the Arbortext PE サブプロセス has been removed from the operating system. The deletion is attempted every time the work thread runs until the deletion succeeds. Temporary directory deletion releases the disk space used for processing requests that the Arbortext PE サブプロセス had consumed.