EDG3X71 can only be called from the JES3 exit IATUX71. If EDG3X71 is called when DFSMSrmm is not started or in use, EDG3X71 sets return code 0 for IATUX71. EDG3X71 determines whether information should be inserted or appended for JES3 messages and determines the value to be used for MSGDISP tape drive display processing.

To check that the IATUX71 exit modification is installed correctly, you can run some batch jobs that use both specific and nonspecific tape requests. You should check that messages displayed on the consoles, in SYSLOG, in DLOG and MLOG, and in JESMSG contains the expected DFSMSrmm updates.