The recommended method of upgrading existing dictionaries or
  repositories is to use the CDD$UPGRADE.COM command procedure.  The
  CDD$UPGRADE.COM command procedure automatically invokes the appropriate
  upgrade utility based on the version number you specify.  The procedure
  is provided with the Oracle CDD/Repository installation.

  If you are performing an upgrade from a Version 5.n repository to a
  later Version 5.n or higher repository, CDD$UPGRADE.COM runs the CDO
  CONVERT utility using the CDO CONVERT/REPOSITORY command.  This is
  referred to as a minor upgrade.

  In Version 5.0, the upgrade portion of the CONVERT command was
  disabled.  However, in Version 5.1 and later, CDO CONVERT/REPOSITORY
  can be used to perform a minor upgrade.

  If you are performing an upgrade from a Version 4.n dictionary, the
  CDD$UPGRADE.COM procedure runs CDDX, the repository translation
  utility, using the REPOSITORY EXPORT and REPOSITORY IMPORT commands.
  This type of upgrade is referred to as a major upgrade.

  Note:  DMU dictionaries do not require an upgrade.

  The CDD$UPGRADE.COM procedure and the REPOSITORY IMPORT and REPOSITORY
  EXPORT commands must be invoked from the DCL level.  See the CDDX help
  topic for information on the REPOSITORY IMPORT and REPOSITORY EXPORT
  commands.

  You invoke the CONVERT/REPOSITORY command from CDO.  See the
  description of the CDO CONVERT command in the CDO utility online help.