The API does provide some limited debugging facilities which may help in tracking down unusual behavior. The routine PMDF_debug may be called to enable debugging output for either enqueuing or dequeuing operations. On OpenVMS systems, all debugging output is written to PMDF_OUTPUT if defined or to SYS$OUTPUT otherwise. On UNIX and NT systems, debugging output is written to stdout.
PMDF_debug should be called after either PMDF_enqueue_initialize or PMDF_dequeue_initialize or both have been called.
Further debugging output may be enabled by setting OS_DEBUG=1 in the PMDF option file.
Message enqueue and dequeue activities performed through the PMDF API
(and callable SEND) will be logged when the channels involved are
marked with the
logging channel keyword.