GATE CS 2026 Set 2 Q.20: Transactions, Serializability and Concurrency Control

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?

Both $T_1$ and $T_2$ only read $A$

$T_1$ reads $A$ and $T_2$ writes $A$

$T_1$ writes $A$ and $T_2$ reads $A$

Both $T_1$ and $T_2$ write $A$

Official answer and solution

Official answer: A
From: Official GATE 2026 answer key

Solution

Recall the definition of conflicting operations in concurrency control: two operations on the same data item conflict if and only if at least one of them is a write.

Two operations by different transactions on the same data item $A$ conflict if at least one of them is a write (giving Read-Write, Write-Read, or Write-Write conflicts). They do not conflict if and only if both transactions only perform read operations on $A$ (Read-Read).

Final answer

Option (A)

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2026 Computer Science and Information Technology - Session 2 (CS2)
Question: 20 of 65
Section: Computer Science and Information Technology

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