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DBMS GATEBOOK Exam_48

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For the given below schedule, which of the following statements is false. (Assume Time stamp of Ti is i)

T1 T2 T3 T4
R1(A)      
  R1(A)    
    W1(A)  
      R1(A)
W1(A)      
Commit      
  W1(A)    
      W1(A)
      Commit
    R1(A)  
  R2(A)    
  W2(A)    
  Commit    
    Rollback  

(A) It is not conflict serializable
(B) It is not view serializable also, because there are no blind writes
(C) The first operation that is going to be failed under Thomas write rule is  W1(A) of T1
(D) The above schedule will be cascading rollback.

WHAT IS THE ANSWER FOR THIS QUES? 

1 Answer

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Answer D.

T4 reads from T3 but commits first even before T3 commits. Now, T3 rolls back. Now, we cant roll back T4(which has read value from T3) since it has already committed. So, this schedule is non-recoverable schedule.

Hence, no question of cascading rollback(since cascading rollback schedule needs to be recoverable schedule).

Hence, (D).
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