The GATE Grind

GATE 2025 CS (CS1) – Question 15

Databases · Transactions and Concurrency Control · 1 mark · Multiple choice

A schedule of three database transactions $T_1$, $T_2$, and $T_3$ is shown. $R_i(A)$ and $W_i(A)$ denote read and write of data item $A$ by transaction $T_i$, $i = 1,2,3$. The transaction $T_1$ aborts at the end. Which other transaction(s) will be required to be rolled back?

$R_1(X)\ W_1(Y)\ R_2(X)\ R_2(Y)\ R_3(Y)\ ABORT(T_1)$

  1. Only $T_2$
  2. Only $T_3$
  3. Both $T_2$ and $T_3$
  4. Neither $T_2$ nor $T_3$

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Show answer and explanation

Correct answer: (C) Both $T_2$ and $T_3$

Explanation

T1 writes Y, and both T2 and T3 read Y before T1 aborts. These are dirty reads, so both must be rolled back (cascading abort).