GATE 2010 CS (CS1) – Question 52

Databases · Transactions and Concurrency Control · 2 marks · Multiple choice

Find the equivalent serial order for this schedule, listed from first operation to last:

r1(X), r2(Y), r3(Y), w2(Y),
w1(X), w3(X), r2(X), w2(X)

T1→T3→T2
T2→T1→T3
T2→T3→T1
T3→T1→T2

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Show answer and explanation

Correct answer: (A) T1→T3→T2

Explanation

Conflicts on X give T1→T3, T1→T2 and T3→T2. On Y, r3(Y) precedes w2(Y), also giving T3→T2. The resulting acyclic precedence graph has the topological order T1,T3,T2. Hence A.

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