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Gradiance Online Accelerated Learning
Spring-21 HW8
Number of questions: 5 Positive points per question: 20.0 Negative points per question: 0.0
1. Consider the following schedule of operations:
r1(X), r1(Y), w1(Y), r2(Z), w1(X), r3(X), w3(X), w2(Z)
Which of the following schedules is conflict equivalent to this schedule?
a) r1(X), r1(Y), r2(Z), w1(Y), w2(Z), w1(X), r3(X), w3(X)
b) r1(Y), r1(X), w1(Y), r2(Z), r3(X), w3(X), w1(X), w2(Z)
c) r1(X), r1(Y), w1(Y), r2(Z), r3(X), w1(X), w3(X), w2(Z)
d) r1(Y), r1(X), w1(Y), r3(X), w1(X), r2(Z), w3(X), w2(Z)
2. Consider the following transactions: T1: r1(X), r1(Y), w1(Y)
T2: r2(X), w2(X), r2(Y)
Which of the following is a TRUE statement about schedules involving the operations of T1 and T2?
a) There are exactly 6 schedules that are conflict equivalent to (T1, T2)
b) There are exactly 7 conflict-serializable schedules
c) There are exactly 4 schedules that are conflict equivalent to (T2, T1)
d) There are exactly 5 schedules that are conflict equivalent to (T2, T1)
3. Consider the following transaction schedule:
r1(X), r1(Y), w1(Y), r2(Z), w1(X), r2(Y), r3(X), w2(Y), w3(X), w2(Z)
Which of the following is a TRUE statement about this schedule?
a) The schedule is conflict-equivalent to (T2, T3, T1)
b) The schedule is conflict-equivalent to (T1, T3, T2)
c) The schedule is conflict-equivalent to (T3, T2, T1)
d) The schedule is conflict-equivalent to (T3, T1, T2)
4. Consider the following schedule S:
r1(X), w1(Y), r2(Y), w2(Z), w1(X), c1, w2(X), c2
Tell whether S is serial? serializable? recoverable? ACR (avoids cascading rollback)? Then, indicate which of the following is TRUE about S?
a) S is serializable and S is recoverable
b) S is serial and S is recoverable
c) S is serial and S does not avoid cascading rollback
d) S is serial and S is not recoverable
5. Which of the following schedules is recoverable, but does not avoid cascading rollback and is not serializable?
a) r1(X), w1(Z), r2(Y), w1(Y), c1, r2(Z), w2(X), w2(Z), c2
b) r1(X), r2(X), w2(Y), r2(Z), r1(Y), w1(X), c1,w2(Z), c2
c) r2(X), r1(X), w1(Z), r2(Z), r1(Y), w1(Y), c1,w2(X), c2
d) r1(X), w1(Y), r2(X), r2(Y), w1(X), c1, w2(Y), w2(Z), c2
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