The ALE Monitor allows you to make inquiries about the processing status of an IDoc in the receiving system actively from within the sending system. In SAP systems of release < 4.6C this can be done with the transaction BDM2 (Cross System IDoc Reporting) and from release 4.6C on with transaction BD87 (Status Monitor for ALE Messages). As inputs you can specify certain selection criteria, like Document Number, Message Type, LS of receiver and date ranges. The system then makes a synchronous RFC call (IDOC_DATE_TIME_GET) to the LS that received the IDocs, with a list of DOCNUMs corresponding to the selected IDocs. (From transaction BD87 you have to hit the toolbar button "Trace IDocs" after the selection of the IDocs.) This function call returns for each IDoc the DOCNUM, under which it was saved in the receiving system, the receiving time and the current processing status in the receiving system.