Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct? A) The same undo and redo list will be used while recovering again. B) The system cannot recover any further. C) All the transactions that are already undone and redone will not be recovered again. D) The database will become inconsistent.

Official answer: A) The same undo and redo list will be used while recovering again.. Explanation: In log-based database recovery without checkpointing: [cite: 1] 1. Idempotency of Recovery: Redo and undo operations are designed to be idempotent, meaning executing them multiple times produces the exact same result as executing them once. 2. State of the Log: Since checkpointing is not performed during normal transaction processing or during recovery, the log on stable storage remains the same as before the recovery started. 3. Recovery Restart: When the system restarts after the second crash, it scans the log from the very beginning. Because the log has not changed and no checkpoint records were inserted, the recovery manager constructs the exact same undo-list and redo-list. Therefore: - (A) is correct: The same undo and redo list will be used while recovering again [cite: 1]. - (B) is incorrect: The system can successfully recover because redo and undo actions are idempotent. - (C) is incorrect: Transactions will be processed again according to the same lists. - (D) is incorrect: Once the recovery process eventually finishes, the database is restored to a consistent state.

A) The same undo and redo list will be used while recovering again.

B) The system cannot recover any further.

C) All the transactions that are already undone and redone will not be recovered again.

D) The database will become inconsistent.

Databases · Transactions and Concurrency Control

Official IIT answer key · IIT Bombay · Audited Aug 2026

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GATE CSE 2021 Set 1 Q13 · MSQ · 1 mark

Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

Select one or more options

Key concept

Transactions and Concurrency Control

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Examiner trap & misconception

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How GATE tests Transactions and Concurrency Control

Across 2012–2026, Transactions and Concurrency Control in GATE CS is heavily weighted towards testing precedence (serialization) graphs for conflict serializability, schedule classification (recoverable, cascadeless, strict), and locking/timestamping protocol mechanics. Questions frequently present interleaved schedules and require students to identify conflict edges, count valid topological orders, or detect recovery anomalies such as dirty reads and cascading rollbacks. Recent exams (2021–2025) feature multiple MSQs testing theoretical invariants of Two-Phase Locking (2PL), deadlock prevention protocols (Wait-Die, Wound-Wait), and real-world ACID violations.

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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

Databases · Transactions and Concurrency Control

Official IIT answer key · IIT Bombay · Audited Aug 2026

Take topic test

GATE CSE 2021 Set 1 Q13 · MSQ · 1 mark

Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

Select one or more options

Key concept

Transactions and Concurrency Control

Step-by-step verified solution

Examiner trap & misconception

Topic notes

How GATE tests Transactions and Concurrency Control

Full Transactions and Concurrency Control guide →

More on Transactions and Concurrency Control

All 25 questions on Transactions and Concurrency Control →

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

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Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

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Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

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Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery. Which of the following statements is/are correct?

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