(a) Locking-based algorithms for concurrency control can be employed to synchronize the execution of transactions. Explain what is meant by a serializable schedule and show that the following locking-based schedule is not serializable:
S = [wl 1 (y), wl 2 (y), R 1 (y), W 1 (y), R 2 (y), W 2 (y), rl 1 (y), rl 2 (y), wl 2 (z), R 2 (z), W 2 (z), rl 2 (z), C 2 ,
wl 1 (z), R 1 (z), W 1 (z), rl 1 (z), C 1 ]
where R i (x)/W i (x) indicates a read/write by transaction i on data item x
rl i (x)/wl i (x) indicates a release/write lock by transaction i on item x
C i indicates a commit operation by transaction i.
(b) Identify the problem with the above schedule, and produce a correct locking-based serializable schedule.

Question

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The Answer of (a) Locking-based algorithms for concurrency control can be employed to synchronize the execution of transactions. Explain what is meant by a serializable schedule and show that the following locking-based schedule is not serializable:
S = [wl 1 (y), wl 2 (y), R 1 (y), W 1 (y), R 2 (y), W 2 (y), rl 1 (y), rl 2 (y), wl 2 (z), R 2 (z), W 2 (z), rl 2 (z), C 2 ,
wl 1 (z), R 1 (z), W 1 (z), rl 1 (z), C 1 ]
where R i (x)/W i (x) indicates a read/write by transaction i on data item x
rl i (x)/wl i (x) indicates a release/write lock by transaction i on item x
C i indicates a commit operation by transaction i.
(b) Identify the problem with the above schedule, and produce a correct locking-based serializable schedule.

(A) Locking-Based Algorithms for Concurrency Control Can Be Employed to Synchronize