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 the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?

Undo: none; Redo; T2, T4, T3, T1

Consider a simple checkpointing protocol and the following set of oper

1.	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 the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?
A.	Undo: T3, T1; Redo: T2
B.	Undo: T3, T1; Redo: T2, T4
C.	Undo: none; Redo; T2, T4, T3, T1
D.	Undo: T3, T1, T4; Redo: T2
Answer» B. Undo: T3, T1; Redo: T2, T4

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