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GATE 2026 CS (CS2) – Question 20

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

Consider concurrent execution of two transactions $T_1$ and $T_2$ in a DBMS, both of which access a data object $A$. For these two transactions to not conflict on $A$, which one of the following statements must be true?

  1. Both $T_1$ and $T_2$ only read $A$
  2. $T_1$ reads $A$ and $T_2$ writes $A$
  3. $T_1$ writes $A$ and $T_2$ reads $A$
  4. Both $T_1$ and $T_2$ write $A$

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Show answer and explanation

Correct answer: (A) Both $T_1$ and $T_2$ only read $A$

Explanation

Two operations conflict if they are from different transactions, access the same data item, and at least one of them is a write. Therefore, the only non-conflicting case is when both transactions only read $A$. Hence, option (A) is correct.