Let Ri(z) and Wi(z) denote read and write operations on a data element z by a transaction Ti, respectively. Consider the schedule S with four transactions.
S: R4(x)R2(x)R3(x)R1(y)W1(y)W2(x)W3(y)R4(y)
Which one of the following serial schedules is conflict equivalent to S?
1
T1 → T3 → T4 → T2
2
T1 → T4 → T3 → T2
3
T4 → T1 → T3 → T2
4
T3 → T1 → T4 → T2