IDF detects program loads, program checks and breakpoints defined by commands for all the tasks running within a partition. To achieve this IDF uses a locking mechanism to single thread each event detected. The lock is in effect from the time the event is detected and is released when control is returned to the respective task. If IDF is interrupted while the LOCK is in effect by a STXIT IT, or STXIT OC for example, a deadlock situation may occur. Take care, when you are debugging subtasks and interruption routines are in effect, that you do not interrupt the IDF session.