Change indicators
      SGU   SEGMENT USAGE DETAILS
      Function: To specify the details of the usage of a segment
                within a message type structure.
010   9166  SEGMENT TAG                                    M  an..3
020   7299  REQUIREMENT DESIGNATOR, CODED                  C  an..3
030   6176  MAXIMUM NUMBER OF OCCURRENCES                  C  n..7
040   7168  LEVEL NUMBER                                   C  n..3
050   1050  SEQUENCE NUMBER                                C  an..10
060   1049  MESSAGE SECTION, CODED                         C  an..3
070   4513  MAINTENANCE OPERATION, CODED                   C  an..3