Hi,

Here is the answer,

A transaction is an atomic unit of work that must be completed in its entirety.The transaction succeeds if it committed and fails if it is aborted.

Database theory has a more rigorous definition of a transaction and states that a transaction has four fundamental properties, known as ACID properties:

A(Atomicity):-The sequence of operations must be atomic, either all or no operations are performed.

C(Consistency):- When completed, the sequence of operations must leave data in consistent mode. All the defined relations/constraints must me Maintained.

I(Isolation): A Transaction must be isolated from all other transactions. A transaction sees the data defore the operations are performed , or after all the operations has performed, it can't see the data in between.

D(Durability): All oprtaions must be permanently placed on the system. Even in the event of system failure , all the operations must be exhibit.

Thanks.