The value of the
message filtering level is set using the given filtering value. If no such level exists, then an error is
reported, STATUS returned set to MSG__IFINV and the current filtering level remains unchanged.
CALL MSG_IFSET( FILTER, STATUS )
FILTER = INTEGER
The filtering level. This may be one of three levels defined in the MSG_PAR include
STATUS = INTEGER (Given and Returned)
The global status.