Editing Database transaction (section)

{{Short description|Unit of work performed within a database management system}}
{{More citations needed|date=August 2010}}

A '''database transaction''' symbolizes a [[unit of work]], performed within a [[database management system]] (or similar system) against a [[database]], that is treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in a database. Transactions in a database environment have two main purposes:

# To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure. For example: when execution prematurely and unexpectedly stops (completely or partially) in which case many operations upon a database remain uncompleted, with unclear status.
# To provide isolation between programs accessing a database concurrently. If this isolation is not provided, the programs' outcomes are possibly erroneous.

In a database management system, a transaction is a single unit of logic or work, sometimes made up of multiple operations. Any logical calculation done in a consistent mode in a database is known as a transaction. One example is a transfer from one bank account to another: the complete transaction requires subtracting the amount to be transferred from one account and adding that same amount to the other.

A database transaction, by definition, must be [[Atomicity (database systems)|atomic]] (it must either be complete in its entirety or have no effect whatsoever), [[Consistency (database systems)|consistent]] (it must conform to existing constraints in the database), [[Isolation (database systems)|isolated]] (it must not affect other transactions) and [[Durability (database systems)|durable]] (it must get written to persistent storage).<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/aa366402(VS.85).aspx|title=What is a Transaction? (Windows)|website=msdn.microsoft.com|date=7 January 2021 }}</ref> Database practitioners often refer to these properties of database transactions using the acronym [[ACID]].