Answer : Option A
Conflict operations:
- Transaction $T_i$ reading data item K, after that Transaction $T_j$ writing data item K
- Transaction $T_i$ writing data item K, after that Transaction $T_j$ reading data item K
- Transaction $T_i$ writing data item K, after that Transaction $T_j$ writing data item K.
Note that, Transaction $T_i$ writing data item ‘K’, after that Transaction $T_j$ writing data item ‘P’ are not conflict operations due to those are different data items.
Tabular representation of given schedule is :
If you observe,
- Line 1 and Line 6 are conflict operations. So in Serial schedule Transaction $T_4$ must be before $T_2$
- Line 3 and Line 6 are conflict operations. So in Serial schedule Transaction $T_3$ must be before $T_2$
- Line 4 and Line 7 are conflict operations. So in Serial schedule Transaction $T_1$ must be before $T_3$
- Line 5 and Line 8 are conflict operations. So in Serial schedule Transaction $T_1$ must be before $T_4$
- Line 7 and Line 8 are conflict operations. So in Serial schedule Transaction $T_3$ must be before $T_4$
Accumulating all these points and running Topological sort, $T_1$ should be first followed by $T_3,T_4$ and $T_2$ in order.