A set of interrelated operations that must all succeed in order for any of them to succeed. Failure of any operation results in a rollback of all operations in the transaction.
In computer science, transaction processing is information processing that is divided into individual, indivisible operations, called transactions. Each transaction must succeed or fail as a complete unit; it cannot remain in an intermediate state.
Transaction processing is designed to maintain a system's Integrity (typically a database or some modern filesystems) in a known, consistent state, by ensuring that interdependent operations on the system are either all completed successfully or all canceled successfully.
Since most, though not necessarily all, transaction processing today is interactive the term is often treated as synonymous with online transaction processing