Test by Bikram | Databases | Test 2 | Question: 21

Question

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:

• A. Atomicity
• B. Consistency
• C. Isolation
• D. Durability

Answer 1

The database must remain in a consistent state after any transaction. No transaction should have any adverse effect on the data residing in the database. If the database was in a consistent state before the execution of a transaction, it must remain consistent after the execution of the transaction as well. 

Ans:B