Editing ACID (section)

=== Atomicity ===
Atomicity is the guarantee that series of database operations in an atomic transaction will either all occur (a successful operation), or none will occur (an unsuccessful operation). The series of operations cannot be separated with only some of them being executed, which makes the series of operations "indivisible". A guarantee of atomicity prevents updates to the database from occurring only partially, which can cause greater problems than rejecting the whole series outright. In other words, atomicity means indivisibility and irreducibility.<ref>{{Cite web |url=https://docs.oracle.com/cd/E17276_01/html/programmer_reference/transapp_atomicity.html |title=Atomicity |website=docs.oracle.com |access-date=2016-12-13}}</ref> Alternatively, we may say that a logical transaction may be composed of several physical transactions. Unless and until all component physical transactions are executed, the logical transaction will not have occurred. 

An example of an atomic transaction is a monetary transfer from bank account A to account B. It consists of two operations, withdrawing the money from account A and depositing it to account B. We would not want to see the amount removed from account A before we are sure it has also been transferred into account B. Performing these operations in an atomic transaction ensures that the database remains in a [[Data consistency|consistent state]], that is, money is neither debited nor credited if either of those two operations fails.<ref>{{cite web
| url = http://archive.oreilly.com/pub/a/onjava/2001/11/07/atomic.html
| url-status = dead
| archive-url = https://web.archive.org/web/20160303090517/http://archive.oreilly.com/pub/a/onjava/2001/11/07/atomic.html
| archive-date = 2016-03-03
| title = Atomic File Transactions, Part 1
| last = Amsterdam
| first = Jonathan
| website = O'Reilly
| access-date = 2016-02-28
}}</ref>