ACID

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In computer science, ACID (atomicity, consistency, isolation, durability) is a set of properties that guarantee database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction. For example, a transfer of funds from one bank account to another, even though that might involve multiple changes (such as debiting one account and crediting another), is a single transaction.

Jim Gray defined these properties of a reliable transaction system in the late 1970s and developed technologies to automatically achieve them.[1] In 1983, Andreas Reuter and Theo Haerder coined the acronym ACID to describe them.[2]

Contents

Characteristics

Atomicity

Atomicity requires that database modifications must follow an "all or nothing" rule. Each transaction is said to be atomic. If one part of the transaction fails, the entire transaction fails and the database state is left unchanged. It is critical that the database management system maintain the atomic nature of transactions in spite of any application, DBMS (Database Management System), operating system or hardware failure.

An atomic transaction cannot be subdivided and must be processed in its entirety or not at all. Atomicity means that users do not have to worry about the effect of incomplete transactions.

Transactions can fail for several kinds of reasons:

Consistency

It ensures the truthfulness of the database.

The consistency property ensures that any transaction the database performs will take it from one consistent state to another.

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