An audit of a banking transactions system has found that on an earlier occasion, two joint holders of account $A$ attempted simultaneous transfers of Rs. 10000 each from account $A$ to account $B$. Both transactions read the same value, Rs. 11000, as the initial balance in $A$ and were allowed to go through. $B$ was credited Rs. 10000 twice. $A$ was debited only once and ended up with a balance of Rs. 1000. Which of the following properties is/are certain to have been violated by the system?

A schedule of three database transactions $T_1, T_2$, and $T_3$ is shown. $R_i(A)$ and $W_i(A)$ denote read and write of data item $A$ by transaction $T_i, i=1,2,3$. The transaction $T_1$ aborts at the end. Which other transaction(s) will be required to be rolled back?

$$R_1(X) W_1(Y) R_2(X) R_2(Y) R_3(Y) \operatorname{ABORT}\left(T_1\right)$$

Once the DBMS informs the user that a transaction has been successfully completed, its effect should persist even if the system crashes before all its changes are reflected on disk. This property is called

Which of the following statements about the Two Phase Locking (2PL) protocol is/are TRUE?