CS3402 Database Systems Tutorials
CS3402 Tutorial 8:
1. Which of the following schedules is (conflict) serializable? For each serializable schedule, determine the equivalent serial schedules.
(a) r1(X); r3(X); w1(X); r2(X); w3(X); (b) r1(X); r3(X); w3(X); w1(X); r2(X); (c) r3(X); r2(X); w3(X); r1(X); w1(X);
2. Consider the following concurrent schedule. Draw the serialization graph for the schedule. Is it conflict serializable?
Ta
Tb
Tc
Read(x)
Write(y)
Read(y)
Write(y)
Write(x)
Commit
Write(z)
Commit
Commit
3. Consider schedules S1, S2 and S3 below. Determine whether each schedule is strict, cascadeless, recoverable, or nonrecoverable. Determine the strictest recoverability condition that each schedule satisfies.
(a) r1(X); w1(X); r2(X); r1(Y); w2(X); c2; c1;
(b) r1(X); w1(X); r2(X); r1(Y); w2(X); w1(Y); c1; c2; (c) r1(X); w1(X); w2(X); w1(Y); c1; r2(X); c2;
Can you change c) into a strict schedule?