Editing Transaction log (section)

{{short description|History of actions executed by a database management system}}
{{redirect|Binary log|the logarithm to base 2|Binary logarithm}}
{{redirect|Journal (computing)| | Journal (disambiguation)}}
{{Prose|date=June 2015}}
In the field of [[database]]s in [[computer science]], a '''transaction log''' (also '''transaction journal''', '''database log''', '''binary log''' or '''audit trail''') is a history of actions executed by a [[database management system]] used to guarantee [[ACID]] properties over [[crash (computing)|crash]]es or hardware failures. Physically, a log is a [[computer file|file]] listing changes to the database, stored in a stable storage format.

If, after a start, the database is found in an [[Consistency (database systems)|inconsistent]] state or not been shut down properly, the database management system reviews the database logs for [[commit (data management)|uncommitted]] transactions and [[rollback (data management)|rolls back]] the changes made by these [[Database transaction|transaction]]s. Additionally, all transactions that are already committed but whose changes were not yet materialized in the database are re-applied. Both are done to ensure [[atomicity (database systems)|atomicity]] and [[durability (computer science)|durability]] of transactions.

This term is not to be confused with other, human-readable [[Log file|logs]] that a database management system usually provides.
<!-- WP:PROVEIT In [[computer storage]], a '''journal''' is a [[Chronology|chronological]] record of [[data processing]] operations that may be used to construct or reinstate an historical or alternative version of a [[computer system]] or [[computer file]]. -->

In [[database management system]]s, a journal is the record of data altered by a given process.<ref>[https://msdn.microsoft.com/en-us/library/ms190925.aspx Microsoft, The Transaction Log (SQL Server)]</ref><ref>[http://www.sqlshack.com/beginners-guide-sql-server-transaction-logs/ sqlshack.com, A beginner’s guide to SQL Server transaction logs, February 11, 2014 by Ivan Stankovic]</ref><ref>[http://www.techrepublic.com/article/understanding-the-importance-of-transaction-logs-in-sql-server/ techrepublic.com, Understanding the importance of transaction logs in SQL Server, SQL Server transaction log maintenance, By Crowe, Chizek, November 11, 2004]</ref><ref>[https://www.neurobs.com/pres_docs/html/03_presentation/07_data_reporting/01_logfiles/index.html neurobs.com, Logfiles]</ref>