Atomicity (database Systems)

Atomicity (database Systems)

In database systems, atomicity (or atomicness; from Greek a-tomos, undividable) is one of the ACID transaction properties. In an atomic transaction, a series of database operations either all occur, or nothing occurs. 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.

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

An example of atomicity is ordering an airline ticket where two actions are required: payment, and a seat reservation. The potential passenger must either:

1. both pay for and reserve a seat; OR
2. neither pay for nor reserve a seat.

The booking system does not consider it acceptable for a customer to pay for a ticket without securing the seat, nor to reserve the seat without payment succeeding.

Another example: If one wants to transfer some amount of money from one account to another, then he/she would start a procedure to do it. However, if a failure occurs, then due to atomicity, the amount will either be transferred completely or will not even start. Thus atomicity protects the user from losing money due to a failed transaction.