Controls whether a new reference copy of an element is created or
    deleted.  If you specify /REFERENCE_COPY, CMS creates a new
    reference copy of the element in the reference copy directory and
    updates the current reference copy directory whenever you create a
    new main line generation of the element.  If you specify
    /NOREFERENCE_COPY, CMS deletes the existing reference copy of the
    element.  The reference copy directory must be established before
    you issue the MODIFY ELEMENT/REFERENCE_COPY command. Use the MODIFY
    LIBRARY/REFERENCE_COPY command to establish the reference copy
    directory.

    Controls whether CMS creates a new reference copy of an element
    whenever you create a new main line generation of the element. If
    you specify /NOREFERENCE_COPY, CMS deletes the existing reference
    copy.

    To establish the reference copy directory, use the MODIFY
    LIBRARY/REFERENCE_COPY command.