On 1/25/21, 3:07 PM, "Raffenetti, Kenneth J." <[email protected]> wrote: Oh, so if I am reading your clarification correctly above, you are saying I should not invoke the dropped handler until a callback for that safety level has been registered. It is possible then that I might never call the dropped handler. Should I be managing dropped event counts for all safety levels? Let me see if I can give a more concrete example. Let's say I have an event registration handle allocated, and a callback registered for the lowest safety level (NONE). I also have a dropped handler registered. The event itself is generating instances for higher safety levels (MPI_RESTRICTED, THREAD_SAFE), but because there are no handlers registered for those levels, the events are being dropped. Question 1: Should the implementation be recording those dropped events for higher safety levels? The text leads me to believe yes. Question 2: Should the implementation delay calling the dropped handler until a callback satisfying the safety level of the dropped events has been registered? Your clarification leads me to believe yes. Question 3: If I register a MPI_RESTRICTED callback, will the dropped handler then execute to inform me of all the dropped events at that safety level? Question 4: If I instead register a THREAD_SAFE callback, will the dropped handler execute to inform me of all the dropped events at that safety level **as well as MPI_RESTRICTED**? Ken