The READ_WRITE option is used to change a read-only RDB$SYSTEM
    storage area (and the Oracle Rdb system relations stored in the
    area) to read/write. Select the READ_WRITE option to change a
    read-only RDB$SYSTEM storage area to read/write.

    To change a storage area other than the RDB$SYSTEM storage area
    to read/write, or to change a database to read/write, use the
    READ_WRITE option of the change-storage-area-clause.