time stamp ordering

Question

Consider the following sequence of actions.
r1(A) r2(B) w1(C) r3(B) r3(C) w2(B) w3(A)
Which of the following time stamp ordering allowed to execute the schedule using basic time stamp protocol?

A) (T1, T2, T3) = (10, 30, 20)
B) (T1, T2, T3) = (20, 30, 10)
C) (T1, T2, T3) = (30, 20, 10)
D) (T1, T2, T3) = (10, 20, 30)

Answer 1

Consider A-> T1 is reading it and then T3 is writing to it. While reading, R-ts(A) is set to max( R-ts(A), TS (1)). So, if R-ts(A) is So, T3 > T1

Consider B-> T2 is reading it and then T3 is again reading it and T2 is then writing to it. So, T2 > T3 (Reading only updates R-ts and and checks only W-ts)

Consider C -> T1 is writing to it and T3 is reading from it. So, T3 > T1

Thus, T1 < T3 < T2- option (A).

http://courses.cs.vt.edu/~cs5204/fall00/distributedSys/bto.html