The following two questions relate to scheduling:

a) For each of the following schedules, draw the precedence graph and argue if the schedule is conflict serializable. If the schedule is conflict serializable, give one possible equivalent serial schedule. (Ri means transaction i reads an item and Wi writes an item.)

Schedule a) R1(A);W1(A);R2(A);R2(B);W3(B);W2(C);R4(A);R4(B);R4(C);R2(D);R3(E);

Schedule b) R1(A);R4(A);W1(A);W3(B);R2(A);R2(B);W2(C);R4(B);R4(C);R2(D);R3(E);

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b) For the following two schedules, insert the appropriate locks (shared and exclusive) into the schedule following the Strict 2PL protocol. Also explain what happens as the scheduler executes each schedule. Note that, if a transaction blocks because of an operation, the transaction with the next operation in the schedule will continue. If you have a deadlock, you need to chose a transaction to abort, release its locks, and let the rest of the schedule continue. You need to restart the aborted transaction again at some point after it has been aborted. When a transaction unblocks, it resumes its operations. Write the actual executed schedule at the end.

Schedule a) R1(A);R2(B);R3(C);W1(B);W2(C);W3(D);

Schedule b) R1(A);R2(B);R3(C);R1(B);R2(C);R3(A);W1(A);W2(B);W3(C);