1
GATE CSE 2008
+2
-0.6
Consider the following three schedules of transactions T1, T2 and T3.
[ Notation: In the following NYO represents the action Y (R for read, W for write) performed by transac­tion N on object O. ]

(S1) 2RA 2WA 3RC 2WB 3WA 3WC 1RA 1RB 1WA 1WB

(S2) 3RC 2RA 2WA 2WB 3WA 1RA 1RB 1WA 1WB 3WC

(S3) 2RZ 3RC 3WA 2WA 2WB 3WC 1RA 1RB 1WA 1WB

Which of the following statements is TRUE?
A
S1, S2 and S3 are all conflict equivalent to each other
B
No two of S1, S2 and S3 are conflict equivalent to each other
C
S2 is conflict equivalent to S3, but not to S1
D
S1 is conflict equivalent to S2, but not to S3
2
GATE CSE 2007
+2
-0.6
Consider the following schedules involving two transactions. Which one of the following statements is TRUE?

S1: r1(X); r1(Y); r2(Y); r2(X); w2(Y); w1(X);

S2: r1(X); r2(X); r2(Y); w2(Y); r1(Y); w1(X);

A
Both S1 and S2 are conflict serializable.
B
S1 is conflict serializable and S2 is not conflict serializable.
C
S1 is not conflict serializable and S2 is conflict serializable.
D
Both S1 and S2 are not conflict serializable.
3
GATE CSE 2007
+2
-0.6
Consider the following two transactions: T1 and T2.
T1: read (A);                  T2: read (B);
if A = 0 then B ← B + 1;       if B ≠ 0 then A ← A - 1;
write (B);                     write (A);
Which of the following schemes, using shared and exclusive locks, satisfy the requirements for strict two phase locking for the above transactions?
A
S1 : lockS(A); 	        S2 : lockS(B);
lockS(B);               lockS(A);
if A = 0                if B ≠ 0
then B ← B + 1;        then A ← A - 1;
write (B);              write (A);
commit;                 commit;
unlock (A);             unlock (B);
unlock (B);             unlock (A);
B
S1 : lockX(A);          S2 : lockX(B);
lockX(B);               lockX(A);
if A = 0                if B ≠ 0
then B ← B + 1;        then A ← A - 1;
write (B);              write (A);
unlock (A);             unlock (A);
commit;                 commit;
unlock (B);             unlock (A);
C
S1 : lockS(A);           S2 : lockS(B);
lockX(B);                lockX(A);
if A = 0                 if B ≠ 0
then B ← B + 1;         then A ← A - 1;
write (B);               write (A);
unlock (A);              unlock (B);
commit;                  commit;
unlock (B);              unlock (A);
D
S1 : lockS(A);           S2 : lockS(B);
lockX(B);                lockX(A);
if A = 0                 if B ≠ 0
then B ← B + 1;        then A ← A - 1;
write (B);               write (A);
unlock (A);              unlock (A);
unlock (B);              unlock (B);
commit;                  commit;
4
GATE CSE 2004
+2
-0.6
Consider the following schedule S of transactions T1 and T2: Which of the following is TRUE about the schedule S?
A
S is serializable only as T1,T2
B
S is serializable only as T2,T1
C
S is serializable both as T1, T2 and T2, T2
D
S is not serializable either as T1 or as T2
GATE CSE Subjects
EXAM MAP
Medical
NEET