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2 votes
2 votes
T1 T2 T3 T4
  R(X)    
    W(X)  
    C3;  
W(X)      
C1;      
  W(Y)    
  R(Z)    
  C2;    
      R(X)
      R(Y)
      C4;

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Doubt: Transaction T3 is commited before T1 and w-w problem.This results is there any edge between T3 and T1 in precedence graph or not??

1 Answer

Best answer
5 votes
5 votes

Problem comes when there is an edge between

a) Two transactions which ar different

b) The pair is either read write , or write read or write

c) On the same data item

d) The earlier of the two should be uncommitted as the problem does not come on committed transactions.

Keeping in mind the above points , we have following conflict pairs :

a) T2 - T1

c) T2 - T3

edited by

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