Labs 8 - Validation-based and multiversion protocols.
=====================================================

Exercises
=========

(1) Consider the following schedules. Indicate what happens when each schedule
    is processed by a validation-based scheduler.

    Schedule 1
    ---------------------------------
    T1:         T2:         T3:
    read(A,B)
                read(B,C)
    validate
                            read(C,D)
                            validate
    write(A)
                validate
                write(A)
                            write(B)

    Schedule 2
    ---------------------------------
    T1:         T2:         T3:
    read(A,B)
                read(B,C)
    validate
                            read(C,D)
                            validate
    write(A)
                validate
                write(A)
                            write(D)

    Schedule 3
    ---------------------------------
    T1:         T2:         T3:
    read(A,B)
                read(B,C)
                            read(C)
    validate
                validate
                            validate
    write(C)
                write(B)
                            write(A)

(2) Consider the following schedules. Indicate what happens when each schedule 
    is processed by a multiversion scheduler. The transactions start in order.
    What happens if a timestamp scheduler is used?   

    Schedule 1
    -------------------------------------------
    T1:         T2:         T3:         T4:
    write(A)
                write(A)
                            write(A)
                read(A)
                                        read(A)

    Schedule 2
    -------------------------------------------
    T1:         T2:         T3:         T4:
    write(A)
                            write(A)
                                        read(A)
                read(A)

    Schedule 3
    -------------------------------------------
    T1:         T2:         T3:         T4:
    write(A)
                                        write(A)
                            read(A)
                write(A)