Example – Lost update
•
•ClearOut(p1,s1) AcceptReturn(p1,s1,60)
•Query InStore; qty is 25
•Add 25 to WarehouseQty: 40->65
•                          Update row 1: 25->85
•Update row 1, setting it to 0
•COMMIT
•                          COMMIT
Initial state of InStore, Product
Final state of InStore, Product
60 returned p1’s have vanished from system; total is still 135
etc
etc
etc
45
s1
p2
50
s2
p1
25
s1
p1
etc
etc
etc
45
s1
p2
50
s2
p1
0
s1
p1
etc
etc
etc
55
etc
p2
40
etc
p1
etc
etc
etc
55
etc
p2
65
etc
p1