The listener user exit routine receives parameters in a six-word
data structure that is pointed to by register 1 on entry to the listener
user exit routine.
The six-word data structure contains parameters from one or both
of the following sources:
- The system. The first fullword of the data structure contains
the address of the parameter list associated with the ENF event code's
mapping macro. See ENF event codes and meanings for
a list of the mapping macros.
- The ENF listener. The listening program can send parameters to
the listener user exit routine by using the PARM keyword on the ENFREQ
macro. PARM can be either a fullword of data or the address of a
parameter list. PARM is passed to the listener user exit routine
in the third word of the data structure.