Which one of the following is NOT a part of the $$ACID$$ properties of database transactions?

Consider the following transaction involving two bank accounts x and y.

read (x) ; x: = x - 50; write (x); read (y); y: = y + 50;   write (y)

The constraint that the sum of the accounts x and y should remain constant is that of

Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock?

I. 2-phase locking
II. Time-stamp ordering

Amongst the ACID properties of a transaction, the 'Durability' property requires that the changes made to the database by a successful transaction persist