GATE CS 2025 Set 1 — Question 15
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Databases → Transactions & Concurrency → Recoverability
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Question
A schedule of three database transactions , and is shown. and denote read and write of data item by transaction . The transaction aborts at the end. Which other transaction(s) will be required to be rolled back?
Correct answer
(C) Both T₂ and T₃
Solution
To determine which transactions must be rolled back, we look for 'dirty reads'—cases where a transaction reads data written by another transaction that has not yet committed.In the given schedule:
- writes to data item ().
- reads () after has written it but before has committed or aborted. This is a dirty read.
- reads () after has written it but before has committed or aborted. This is also a dirty read.
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