Details of the OBEY transaction which started this action are obtained from the COMMON blocks (DTASK_CMN) then DTASK_APPLIC() is called with context CANCEL and that in turn calls the user's code. See SUN/134 for examples of how the user's code might handle a CANCEL
On return from DTASK_APPLIC the status and REQUEST returned from the application are checked (DTASK_ACT_SCHED()) to see whether the action is to be terminated or is to continue rescheduling. In any case, an acknowledgement is sent to the task which requested the CANCEL. If the action has ended, an acknowledgement is also sent to the task which issued the OBEY.
ADAM The Control Subsystem