Conflict Serializability Assignment - S P SHARMA CLASSES

 

Question 1 : Consider the following schedules involving two transactions. Which one of the following statement is true? 

S1: R1(X) R1(Y) R2(X) R2(Y) W2(Y) W1(X) 
S2: R1(X) R2(X) R2(Y) W2(Y) R1(Y) W1(X) 

• Both S1 and S2 are conflict serializable
• Only S1 is conflict serializable
• Only S2 is conflict serializable
• None

Question 2 : Consider the following schedules involving two transactions. Which one of the following statement is true? 

S1: r1(x) r1(y) w2(x) w1(x) r2(y)
S2: r1(x) r3(y) w1(x) w2(y) r3(x) w2(x)

• Both S1 and S2 are conflict serializable
• Only S1 is conflict serializable
• Only S2 is conflict serializable
• None

Question 3 : Consider the following schedules involving three transactions. Which one of the following statement is true? 

S1: r1(X); r3(Y); r3(X); r2(Y); r2(Z);
    w3(Y); w2(Z); r1(Z); w1(X); w1(Z)
S2: r1(X); r3(Y); r2(Y); r3(X); r1(Z);
    r2(Z); w3(Y); w1(X); w2(Z); w1(Z) 

Which one of the following statements about the schedules is TRUE?
(A) Only S1 is conflict-serializable.
(B) Only S2 is conflict-serializable.
(C) Both S1 and S2 are conflict-serializable.
(D) Neither S1 nor S2 is conflict-serializable.

Question 4 : Let $S$ be the following schedule of operations of three transactions T1, T2 and T3 in a relational database system:

R2(Y),R1(X),R3(Z),R1(Y)W1(X),R2(Z),W2(Y),R3(X),W3(Z)$$$$

Consider the statements P$P$ and Q$Q$ below:

• P: S is conflict-serializable.
• Q: If T3 commits before T1 finishes, then S is recoverable.

Which one of the following choices is correct?

1. Both P and Qare true
2. P is true and Q is false
3. P is false and Q is true
4. Both P and Q are false

1. C

2. C

3. A

4. B