o  You must have the Oracle Rdb DELETE privilege for a field to
       delete the field with the DELETE FIELD statement.

    o  If you want to delete a field that is part of a relation
       definition, you must use the CHANGE RELATION statement to
       delete the field from the relation definition, or you must
       delete the entire relation.

    o  If you want to delete a field that is referred to in a
       constraint or index definition, you must first delete the
       constraint or index.

    o  You cannot delete a field definition unless you have invoked
       the database that includes the field.

    o  You can delete a field definition even when there are
       active users. Deleting a field definition will not affect
       active users until they exit their session and 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.

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