Allows the current session defaults to be specified for query
    optimization characteristics.

    This statement can reset the session defaults using DEFAULT, or
    can specify one or more keywords for SELECTIVITY or FAST FIRST or
    TOTAL TIME optimization.

    This statement affects all subsequent query compiles in
    interactive SQL, or queries specified using dynamic SQL.

    See the Oracle Rdb SQL Reference Manual for information on
    setting the optimization level in SQL module and precompiler
    languages.