Let ri(z) and wi(z) denote read and write operations respectively on a data item z by a transaction Ti. Consider the following two schedules.
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)
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
Neither S1 nor S2 is conflict serializable.
2
GATE CSE 2020
MCQ (Single Correct Answer)
+2
-0.67
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
B
C
D
3
GATE CSE 2016 Set 2
MCQ (Single Correct Answer)
+2
-0.6
Consider the following database schedule with two transactions, T1 and T2
S = r2(X); r1(X); r2(Y); w1(X); r1(Y); w2(X); a1; a2
where ri(Z) denotes a read operation by transaction Ti on a variable Z, wi(Z) denotes a write operation by Ti on a variable Z and ai denotes an abort by transaction Ti
.
Which one of the following statements about the above schedule is TRUE?
A
S is non-recoverable
B
S is recoverable, but has a cascading abort
C
S does not have a cascading abort
D
S is strict
4
GATE CSE 2016 Set 1
MCQ (Single Correct Answer)
+2
-0.6
Consider the following two phase locking protocol. Suppose a transaction $$T$$ accesses (for read or write operations), a certain set of objects $$\left\{ {{O_1},...,{O_k}} \right\}.$$ This is done in the following manner:
Step 1. T acquires exclusive locks to $${{O_1},...,{O_k}}$$ in increasing order of their
addresses.
Step 2. The required operations are performed.
Step 3. All locks are released.
This protocol will
A
guarantee serializability and deadlock-freedom
B
guarantee neither serializability nor deadlock-freedom
C
guarantee serializability but not deadlock-freedom
D
guarantee deadlock-freedom but not serializability
