The CHANGE RECORD command modifies a record element by performing
    a change in place. CDO changes the values you specify, and other
    values remain the same.

    If a record element is controlled, CDO freezes previous versions
    and allows you to modify only the highest visible version. If a
    record element is uncontrolled, CDO modifies the highest version
    unless you specify another version number.

    If a record element is controlled, you must reserve the record
    element before you can issue the CHANGE RECORD command. The
    SHOW RECORD or SHOW RESERVATIONS command indicates whether this
    condition exists.

    When you change a record element that an Oracle Rdb database
    uses, you may need to integrate the database with the repository.
    CDO automatically sends a notice with the name of the database
    when this possibility occurs.

    To remove a field, record, or structure definition from a record
    element, if the definition is not contained within a variant or
    structure definition, specify the DELETE keyword, followed by
    the appropriate name or clause for the type of definition you are
    removing.

    To remove a definition from within a variant definition, use the
    NOVARIANTS and VARIANT keyword, followed by the DELETE clause.

    To remove a definition from within a structure definition,
    specify the CHANGE RECORD Structure Change Clause. Specify the
    DELETE keyword, followed by the name of the definition you are
    removing.

    If you are deleting a constraint, you must delete the
    constraint before you delete the field; they cannot be deleted
    simultaneously using the CHANGE RECORD command. To update
    the change in the database, you must integrate each change
    separately.