Consider the following transaction involving two bank accounts $A$ and $B$.
$\begin{array}{|l|} \hline \text{read(A);} \\ \hline A:=A-250; \\ \hline \text{write(A);} \\ \hline \text{read(B);} \\ \hline B:=B+250; \\ \hline \text{write(B);} \\ \hline \end{array}$
The constraint that the sum of the accounts $A$ and $B$ should remain constant is that of:
- Atomicity
- Consistency
- Isolation
- Durability