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Undo/Redo Logging (cont)

For the example transaction, we might get: 

t    Action        v  B(A)  B(B)  D(A)  D(B)  Log
--------------------------------------------------------
(0)  BEGIN         .    .     .     8     5   <START T>
(1)  READ(A,v)     8    8     .     8     5
(2)  v = v*2      16    8     .     8     5
(3)  WRITE(A,v)   16   16     .     8     5   <T,A,8,16>
(4)  READ(B,v)     5   16     5     8     5
(5)  v = v+1       6   16     5     8     5
(6)  WRITE(B,v)    6   16     6     8     5   <T,B,5,6>
(7)  FlushLog
(8)  StartCommit
(9)  OUTPUT(A)     6   16     6    16     5
(10)                                          <COMMIT T>
(11) OUTPUT(B)     6   16     6    16     6

Note that T is regarded as committed as soon as (10) completes.