Explicitly enables prestarted transactions.

    For most applications, Rdb recommends that you enable prestarted
    transactions. The default is PRESTARTED TRANSACTIONS ARE ON.
    If you use the PRESTARTED TRANSACTIONS ARE ON clause or do not
    specify the PRESTARTED TRANSACTIONS clause, the COMMIT or
    ROLLBACK statement for the previous read/write transaction
    automatically reserves the TSN for the next transaction and
    reduces I/O.