GATE CSE 2022 Q39: Serial schedule conflict equivalent to a four-transaction schedule

Databases
2 marks
MCQ
−2/3 if wrong

Let $R_i(z)$ and $W_i(z)$ denote read and write operations on a data element $z$ by a transaction $T_i$ , respectively. Consider the schedule S with four transactions.

S: $R_4(x) R_2(x) R_3(x) R_1(y) W_1(y) W_2(x) W_3(y) R_4(y)$

Which one of the following serial schedules is conflict equivalent to S?

Try it: multiple choice: exactly one correct option

Wrong answer costs 2/3 mark in GATE.

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Answer: A (official GATE 2022 final answer key)

Concept used: Build the precedence graph from conflicting pairs (same item, different transactions, at least one write) and topologically sort it.

First step: List conflicts on x (reads before $W_2(x)$ ) and on y ( $R_1/W_1$ before $W_3$ , and both before $R_4(y)$ ).

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Source: official GATE 2022 CS question paper and final answer key, organised by IIT Kharagpur. Question paper · Answer key

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GATE CSE 2022 Q39: Serial schedule conflict equivalent to a four-transaction schedule

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