Mode is a value assigned to an outline when it is generated by
    the optimizer. The default mode is 0. Specify a signed integer.

    If you create multiple outlines for a single query, the outlines
    cannot have the same outline mode. When more than one outline
    exists for a query, you can set the RDMS$BIND_OUTLINE_MODE
    logical name to the value of the outline mode for the outline you
    want the optimizer to use. For example, if you have a query that
    runs during the day and at night and you created two outlines for
    the query, you could keep the default outline mode of 0 for the
    outline to be used during the day, and assign an outline mode of
    -1 for the outline to be used at night. By setting the RDMS$BIND_
    OUTLINE_MODE logical name to -1 at night, the appropriate outline
    is run at the appropriate time.

    Valid values for modes are -2,147,483,648 to 2,147,483,647.
    Positive mode values are reserved for future use, so it is
    recommended that you specify a value between 0 and -2,147,483,648
    for the mode value.