91
Optimistic Concurrency Control
(cont)
Case 1: reading overlaps validation/writing
T
2
starts while
T
1
is validating/writing
if some
X
being read by
T
2
is in
WS(T
1
)
then
T
2
may not have read the updated version of
X
so,
T
2
must start again
![[Diagram:Pics/txproc/occ1.png]](Pics/txproc/occ1.png)
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