Transaction


Question 1
Let R_i(z) and W_i(z) denote read and write operations on a data element z by a transaction T_i, respectively. Consider the schedule S with four transactions.

S: R_4(x)R_2(x)R_3(x)R_1(y)W_1(y)W_2 (x)W_3 (y)R_4(y)

Which one of the following serial schedules is conflict equivalent to S?
A
T_1\rightarrow T_3\rightarrow T_4\rightarrow T_2
B
T_1\rightarrow T_4\rightarrow T_3\rightarrow T_2
C
T_4\rightarrow T_1\rightarrow T_3\rightarrow T_2
D
T_3\rightarrow T_1\rightarrow T_4\rightarrow T_2
GATE CSE 2022   Database Management System
Question 2
Let S be the following schedule of operations of three transactions T_1, T_2 \text{ and }T_3 in a relational database system:

R_2(Y), R_1(X), R_3(Z), R_1(Y)W_1(X), R_2(Z), W_2(Y), R_3(X), W_3(Z)

Consider the statements P and Q below:

P: S is conflict-serializable.
Q: If T_3 commits before T_1 finishes, then S is recoverable.

Which one of the following choices is correct?
A
Both P and Q are true
B
P is true and Q is false
C
P is false and Q is true
D
Both P and Q are false
GATE CSE 2021 SET-2   Database Management System


Question 3
Let r_i(z) and w_i(z) denote read and write operations respectively on a data item z by a transaction T_i. Consider the following two schedules.

S1: r_1(x)r_1(y)r_2(x)r_2(y)w_2(y)w_1(x)
S2: r_1(x)r_2(x)r_2(y)w_2(y)r_1(y)w_1(x)

Which one of the following options is correct?
A
S1 is conflict serializable, and S2 is not conflict serializable
B
S1 is not conflict serializable, and S2 is conflict serializable
C
Both S1 and S2 are conflict serializable
D
Niether S1 nor S2 is conflict serializable
GATE CSE 2021 SET-1   Database Management System
Question 4
Suppose a database system crashes again while recovering from a previous crash. Assume checkpointing is not done by the database either during the transactions or during recovery.

Which of the following statements is/are correct?
A
The same undo and redo list will be used while recovering again
B
The system cannot recover any further
C
All the transactions that are already undone and redone will not be recovered again
D
The database will become inconsistent
GATE CSE 2021 SET-1   Database Management System
Question 5
Consider a schedule of transactions T1 and T2:

Here, RX stands for "Read(X)" and WX stands for "Write(X)". Which one of the following schedules is conflict equivalent to the above schedule?
A
A
B
B
C
C
D
D
GATE CSE 2020   Database Management System


There are 5 questions to complete.

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