A reference to a user-defined word is unique if:

    1)  no other name has the same spelling, including hyphenation,
    2)  it is a part of a REDEFINES clause (the reference following the
        word REDEFINES is unique because of clause placement), or
    3)  scoping rules make it unique.

  A name in a hierarchy of names can occur in more than one place in your
  program.  Unless you are redefining it, you must refer to this
  nonunique name using one or more higher-level names in the hierarchy.
  These higher-level names are called qualifiers.  Using them to achieve
  uniqueness of reference is called qualification.

  To make your reference unique, you need not specify all available
  qualifiers for a name, only the one(s) necessary to avoid ambiguity.

  You cannot use the same data-name as:

    1)  The name of an external record and as the name of any other
        external data item in any program contained within or containing
        the program describing the external data record.

    2)  The name of an item possessing the global attribute and as the
        name of any other data item in the program describing the global
        data item.