To change a relation with the CHANGE RELATION statement, you need
    the Oracle Rdb CHANGE privilege for the relation.

    When you execute this statement, Oracle Rdb modifies the named
    field and relation-specific constraint definition(s) within the
    relation definition. All the fields and constraints that you do
    not mention remain the same.

    When you change a relation definition, other users see the
    revised definition only after they invoke the database the next
    time. By default, a database can be opened automatically (that
    is, by any user who invokes the database and executes a data
    manipulation language statement). If the database was modified
    so that it must be manually opened, the RMU/OPEN command must be
    used to open it.

    You must execute the CHANGE RELATION statement in a read/write
    transaction. If you issue this statement when there is no active
    transaction, Oracle Rdb starts a read/write transaction implicitly.

    Other users are allowed to be attached to the database when you
    issue the CHANGE RELATION statement.