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GATE CSE 2024 Session 1 Q46: Serial schedules conflict-equivalent to a three-transaction schedule

Question

Consider the following read-write schedule SS over three transactions T1T_1, T2T_2, and T3T_3, where the subscripts in the schedule indicate transaction IDs:

S:r1(z);w1(z);r2(x);r3(y);w3(y);r2(y);w2(x);w2(y);S: r_1(z); w_1(z); r_2(x); r_3(y); w_3(y); r_2(y); w_2(x); w_2(y);

Which of the following transaction schedules is/are conflict equivalent to SS?

Try it: multiple select: one or more correct options

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Select all correct options. No negative marking, no partial marks.
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Answer: B, C, D (official GATE 2024 final answer key)

Concept used: Conflict equivalence: every topological order of the precedence graph is an equivalent serial schedule.

First step: Find the conflicting pairs: only T3T_3 and T2T_2 conflict (on yy), and T1T_1 touches only zz.

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Source: official GATE 2024 Session 1 CS question paper and final answer key, organised by IISc Bangalore. Question paper · Answer key

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