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Gate2017 ss Q38

0. Two transactions T1 and T2 are given as:
T1: r1(X)w1(X)r1(Y)w1(Y)
T2 : r2(Y)w2(Y)r2(Z)w2(Z)
where ri(V) denotes a read operation by transaction Ti on a variable V and wi(V) denotes a write operation by transaction Ti on a variable V. The total number of conflict serializable schedules that can be formed by T1 and T2 is ______

  • Option : A
  • Explanation :
    Conflict conditions RW WR WW
    ∴ 5 conflicts
    T1 - T2
    a  b  c  d 
    r1(X) w1(X) r1(Y) w1(Y)
    r2(Y) w2(Y) r2(Z) r2(Z)
    1  2  3  4 
    Constraints:
    a<b<c<d
    1<2<3<4
    d<1 (or) 2<c
    only 1 way
    Total = 70 - (12 + 5) = 53
    Therefore total no of, 53 + 1 = 54
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