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Consider the following two schedules:

S1:

R1(X),W2(Y),R2(X),W1(Y),commit1,commit2.

S2:

R1(X),R2(Y),W1(z),commit1,R3(Y), R3(z),W2(Y),W3(X),commit2,commit3.

Which of the above schedules is allowed by 2PL?

1 Answer

1 votes
1 votes

S1: 

       

T1 T2
S(x)  
r(x) X(y)
  w(y)
  S(x)
  r(x)
  release(x),release(y)
X(y)  
w(y)  
r(x)  
release(x),release(y)  
commit commit

S2:

T1 T2 T3
S(x)    
r(x)    
  S(y)  
  r(y)  
X(z)    
w(z)    
release(x),release(z),commit    
    S(y)
    r(y)
    S(z)
    r(z)
    X(x)
    release(y)
  X(y)  
  w(y)  
  release(y)  
    w(x)
    release(x),release(z)
     
  commit  
    commit

 

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