The essential characteristic of transaction processing systems:

Atomicity: All changes that a transaction makes to a database are made permanent, or else are nullified.

Consistency: A successful transaction transforms a database from a previous valid state to a new valid state.

Isolation: Changes that a transaction makes to a database are not visible to other operations until the transaction completes its work.

Durability: Changes that a transaction makes to a database survive future system or media failures.