008D8EFA Field "<field-name>" is part of an OCCURS list, so it
    cannot be used as a key.

    Explanation:

    The field you specified for a key field in DEFINE FILE is part
    of an OCCURS list. That means that either the field itself has
    an OCCURS clause in its definition or a group field that contains
    the field has an OCCURS clause. Since the field you specified
    will occur multiple times in the same record, it cannot be a key.

    User Action:

    If you want to specify a key somewhere within the OCCURS group,
    you must REDEFINE the entire OCCURS group and specify one of the
    redefine fields as the key.