Consider the transactions T1, T2, T3 and the schedules S1 and S2 given below.
T1 : r1(x); r1(z); w1(z)
T2 : r2(y); r2(z); w2(z)
T3 : r2(y); r3(x); w3(y)
S1 : r1(x); r3(y); r3(x); r2(y); r2(z); w3(y); w3(z); r1(z); w1(x); w1(z)
S2 : r1(x); r3(y); r2(y); r3(x); r1(z); r2(z); w3(y); w1(x); w2(z); w1(z)
Which one of the following statements about the schedules is TRUE?

Correct option is A

1. Conflict-Serializability: This concept examines if the transactions in a schedule can be reordered to match a serial execution. Conflict serializability relies on detecting cycles in a precedence graph.
2. Analyzing S1: By constructing a precedence graph for S1, we find no cycles, meaning it can be rearranged into a serial order, thus it is conflict-serializable.
3. Analyzing S2: For S2, a precedence graph reveals cycles, implying it cannot be rearranged into a conflict-serializable schedule.
Information Booster:
· Conflict Serializability: Ensures that even with concurrent execution, the result is as if the transactions ran in a specific serial order.
· Precedence Graph: A directed graph used to determine conflict-serializability by depicting dependencies among transactions.
Here is the precedence graph for Schedule S1, illustrating the conflict relationships among transactions T1, T2 and T3. Each directed edge represents a conflict dependency, indicating that one transaction’s action affects another, leading to a precedence constraint.