The GATE Grind

GATE 2021 CS – Question 23

Databases · Transactions and Concurrency Control · 1 mark · Multiple select

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?

  1. The same undo and redo list will be used while recovering again.
  2. The system cannot recover any further.
  3. All the transactions that are already undone and redone will not be recovered again.
  4. The database will become inconsistent.

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Show answer and explanation

Correct answer: (A) The same undo and redo list will be used while recovering again.

Explanation

Without checkpoints, recovery restarts from the same log, so the same undo/redo lists are used. Undo/redo are idempotent, so recovery can be repeated and the database stays consistent.