Atomicity (database systems)

In database systems, atomicity (or atomicness; from Greek a-tomos, undividable) is one of the ACID transaction properties. An atomic transaction is a series of database operations such that either all occur, or nothing occurs. The series of operations cannot be divided apart and executed partially from each other, which makes the series of operations "indivisible", hence the name. A guarantee of atomicity prevents updates to the database occurring only partially, which can cause greater problems than rejecting the whole series outright. In other words, atomicity means indivisibility and irreducibility. As a consequence, the transaction cannot be observed to be in progress by another database client. At one moment in time, it has not yet happened, and at the next it has already occurred in whole (or nothing happened if the transaction was cancelled in progress).

The etymology of the phrase originates in the Classical Greek concept of a fundamental and indivisible component; see atom.