To begin monitoring a particular list, you invoke the IXLLIST macro with REQUEST=MONITOR_LIST and ACTION=START. You also specify the list number (LISTNUM) of the list to be monitored and the index of the list notification vector entry (VECTORINDEX) to be associated with the monitored list.

If you want to have your list transition exit receive control when the list changes from empty to nonempty, specify DRIVEEXIT=YES. If you omit the DRIVEEXIT parameter or code DRIVEEXIT=NO, you indicate your intention to monitor the list's transitions by a different means.

When you start transition monitoring of a list, the system initializes the associated vector entry to indicate the current state of the list: empty or nonempty.