GATE | CS | 2015 | Set 2 | Databases | Transaction & Concurrency Control | Question 17

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