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Consider a Simple Checkpointing Protocol and the following set of operations in the log. (start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (Checkpoint); (start, T2); (write, T2, x, 1, 9); (commit, T2); start, T3); (write, T3, z, 7, 2); if a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?

Consider a Simple Checkpointing Protocol and the following set of operations in the log. (start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (Checkpoint); (start, T2); (write, T2, x, 1, 9); (commit, T2); start, T3); (write, T3, z, 7, 2); if a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list? Correct Answer Undo : T3, T1; Redo T2

The correct answer is option 1

T2 must be redone.
T1 and T3 must be undone.

Hint

Transactions that are committed before the latest checkpoint needs neither undo nor redo.
Transactions that are committed after the latest checkpoint need to be redone.
Transactions that are yet to be committed needs to be undone.

Related Questions

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