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id="toc-Characteristics-sublist" class="vector-toc-list"> <li id="toc-Atomicity" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Atomicity"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Atomicity</span> </div> </a> <ul id="toc-Atomicity-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Consistency" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Consistency"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Consistency</span> </div> </a> <ul id="toc-Consistency-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Isolation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Isolation"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Isolation</span> </div> </a> <ul id="toc-Isolation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Durability" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Durability"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.4</span> <span>Durability</span> </div> </a> <ul id="toc-Durability-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Examples" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Examples</span> </div> </a> <button aria-controls="toc-Examples-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Examples subsection</span> </button> <ul id="toc-Examples-sublist" class="vector-toc-list"> <li id="toc-Atomicity_2" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Atomicity_2"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Atomicity</span> </div> </a> <ul id="toc-Atomicity_2-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Consistency_failure" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Consistency_failure"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Consistency failure</span> </div> </a> <ul id="toc-Consistency_failure-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Isolation_failure" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Isolation_failure"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Isolation failure</span> </div> </a> <ul id="toc-Isolation_failure-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Durability_failure" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Durability_failure"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.4</span> <span>Durability failure</span> </div> </a> <ul id="toc-Durability_failure-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Implementation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Implementation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Implementation</span> </div> </a> <button aria-controls="toc-Implementation-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Implementation subsection</span> </button> <ul id="toc-Implementation-sublist" class="vector-toc-list"> <li id="toc-Locking_vs._multiversioning" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Locking_vs._multiversioning"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Locking vs. multiversioning</span> </div> </a> <ul id="toc-Locking_vs._multiversioning-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Distributed_transactions" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Distributed_transactions"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Distributed transactions</span> </div> </a> <ul id="toc-Distributed_transactions-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet 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interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/ACID" title="ACID – Azerbaijani" lang="az" hreflang="az" data-title="ACID" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/ACID" title="ACID – Belarusian" lang="be" hreflang="be" data-title="ACID" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/ACID" title="ACID – Catalan" lang="ca" hreflang="ca" data-title="ACID" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/ACID" title="ACID – Czech" lang="cs" hreflang="cs" data-title="ACID" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/ACID-transaktion" title="ACID-transaktion – Danish" lang="da" hreflang="da" data-title="ACID-transaktion" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/ACID" title="ACID – German" lang="de" hreflang="de" data-title="ACID" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/ACID" title="ACID – Greek" lang="el" hreflang="el" data-title="ACID" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/ACID" title="ACID – Spanish" lang="es" hreflang="es" data-title="ACID" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%A7%D8%B3%DB%8C%D8%AF_(%D9%BE%D8%A7%DB%8C%DA%AF%D8%A7%D9%87_%D8%AF%D8%A7%D8%AF%D9%87)" title="اسید (پایگاه داده) – Persian" lang="fa" hreflang="fa" data-title="اسید (پایگاه داده)" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Propri%C3%A9t%C3%A9s_ACID" title="Propriétés ACID – French" lang="fr" hreflang="fr" data-title="Propriétés ACID" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/ACID" title="ACID – Korean" lang="ko" hreflang="ko" data-title="ACID" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/ACID_(ra%C4%8Dunarstvo)" title="ACID (računarstvo) – Croatian" lang="hr" hreflang="hr" data-title="ACID (računarstvo)" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/ACID" title="ACID – Icelandic" lang="is" hreflang="is" data-title="ACID" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/ACID" title="ACID – Italian" lang="it" hreflang="it" data-title="ACID" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/ACID" title="ACID – Hebrew" lang="he" hreflang="he" data-title="ACID" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/ACID" title="ACID – Hungarian" lang="hu" hreflang="hu" data-title="ACID" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%86%E0%B4%B8%E0%B4%BF%E0%B4%A1%E0%B5%8D_%E0%B4%97%E0%B5%81%E0%B4%A3%E0%B4%B5%E0%B4%BF%E0%B4%B6%E0%B5%87%E0%B4%B7%E0%B4%99%E0%B5%8D%E0%B4%99%E0%B5%BE" title="ആസിഡ് ഗുണവിശേഷങ്ങൾ – Malayalam" lang="ml" hreflang="ml" data-title="ആസിഡ് ഗുണവിശേഷങ്ങൾ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/ACID" title="ACID – Mongolian" lang="mn" hreflang="mn" data-title="ACID" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/ACID" title="ACID – Dutch" lang="nl" hreflang="nl" data-title="ACID" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/ACID_(%E3%82%B3%E3%83%B3%E3%83%94%E3%83%A5%E3%83%BC%E3%82%BF%E7%A7%91%E5%AD%A6)" title="ACID (コンピュータ科学) – Japanese" lang="ja" hreflang="ja" data-title="ACID (コンピュータ科学)" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Atomisk,_konsistent,_isolert,_durabel" title="Atomisk, konsistent, isolert, durabel – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Atomisk, konsistent, isolert, durabel" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/ACID" title="ACID – Polish" lang="pl" hreflang="pl" data-title="ACID" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/ACID" title="ACID – Portuguese" lang="pt" hreflang="pt" data-title="ACID" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/ACID" title="ACID – Russian" lang="ru" hreflang="ru" data-title="ACID" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/ACID" title="ACID – Simple English" lang="en-simple" hreflang="en-simple" data-title="ACID" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/ACID_(%D1%80%D0%B0%D1%87%D1%83%D0%BD%D0%B0%D1%80%D1%81%D1%82%D0%B2%D0%BE)" title="ACID (рачунарство) – Serbian" lang="sr" hreflang="sr" data-title="ACID (рачунарство)" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/ACID" title="ACID – Finnish" lang="fi" hreflang="fi" data-title="ACID" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%85%E0%AE%A3%E0%AF%81%E0%AE%AE%E0%AF%88,_%E0%AE%9A%E0%AF%80%E0%AE%B0%E0%AF%8A%E0%AE%B0%E0%AF%81%E0%AE%AE%E0%AF%88,_%E0%AE%A4%E0%AE%A9%E0%AE%BF%E0%AE%AE%E0%AF%88,_%E0%AE%A8%E0%AE%BF%E0%AE%B2%E0%AF%88%E0%AE%AA%E0%AF%8D%E0%AE%AA%E0%AF%81" title="அணுமை, சீரொருமை, தனிமை, நிலைப்பு – Tamil" lang="ta" hreflang="ta" data-title="அணுமை, சீரொருமை, தனிமை, நிலைப்பு" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/ACID" title="ACID – Ukrainian" lang="uk" hreflang="uk" data-title="ACID" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/ACID" title="ACID – Vietnamese" lang="vi" hreflang="vi" data-title="ACID" 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class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Robustness properties for database transactions</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="/wiki/Acid_(disambiguation)" class="mw-disambig" title="Acid (disambiguation)">Acid (disambiguation)</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output 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0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/ACID" title="Special:EditPage/ACID">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22ACID%22">"ACID"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22ACID%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22ACID%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22ACID%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22ACID%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22ACID%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">May 2018</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>In <a href="/wiki/Computer_science" title="Computer science">computer science</a>, <b>ACID</b> (<a href="/wiki/Atomicity_(database_systems)" title="Atomicity (database systems)">atomicity</a>, <a href="/wiki/Consistency_(database_systems)" title="Consistency (database systems)">consistency</a>, <a href="/wiki/Isolation_(database_systems)" title="Isolation (database systems)">isolation</a>, <a href="/wiki/Durability_(database_systems)" title="Durability (database systems)">durability</a>) is a set of properties of <a href="/wiki/Database_transaction" title="Database transaction">database transactions</a> intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of <a href="/wiki/Database" title="Database">databases</a>, a sequence of database operations that satisfies the ACID properties (which can be perceived as a single logical operation on the data) is called a <i>transaction</i>. For example, a transfer of funds from one bank account to another, even involving multiple changes such as debiting one account and crediting another, is a single transaction. </p><p>In 1983,<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Andreas_Reuter" title="Andreas Reuter">Andreas Reuter</a> and <a href="/wiki/Theo_H%C3%A4rder" title="Theo Härder">Theo Härder</a> coined the acronym <i>ACID</i>, building on earlier work by <a href="/wiki/Jim_Gray_(computer_scientist)" title="Jim Gray (computer scientist)">Jim Gray</a><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> who named atomicity, consistency, and durability, but not isolation, when characterizing the transaction concept. These four properties are the major guarantees of the transaction paradigm, which has influenced many aspects of development in <a href="/wiki/Database_management_system" class="mw-redirect" title="Database management system">database systems</a>. </p><p>According to Gray and Reuter, the <a href="/wiki/IBM_Information_Management_System" title="IBM Information Management System">IBM Information Management System</a> supported ACID transactions as early as 1973 (although the acronym was created later).<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>BASE stands for basically available, soft state, and <a href="/wiki/Eventual_consistency" title="Eventual consistency">eventually consistent</a>: the acronym highlights that BASE is opposite of ACID, like their chemical equivalents.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> ACID databases prioritize <a href="/wiki/Consistency_(database_systems)" title="Consistency (database systems)">consistency</a> over <b>availability</b> — the whole <a href="/wiki/Database_transaction" title="Database transaction">transaction</a> fails if an error occurs in any step within the transaction; in contrast, BASE databases prioritize <b>availability</b> over <b>consistency</b>: instead of failing the transaction, users can access inconsistent data <b>temporarily</b>: data consistency is achieved, but <b>not immediately</b>.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Characteristics">Characteristics</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=1" title="Edit section: Characteristics"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The characteristics of these four properties as defined by Reuter and Härder are as follows: </p> <div class="mw-heading mw-heading3"><h3 id="Atomicity">Atomicity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=2" title="Edit section: Atomicity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Atomicity_(database_systems)" title="Atomicity (database systems)">Atomicity (database systems)</a></div> <p><a href="/wiki/Database_transaction" title="Database transaction">Transactions</a> are often composed of multiple <a href="/wiki/SQL_syntax" title="SQL syntax">statements</a>. <a href="/wiki/Atomicity_(database_systems)" title="Atomicity (database systems)">Atomicity</a> guarantees that each transaction is treated as a single "unit", which either succeeds completely or fails completely: if any of the statements constituting a transaction fails to complete, the entire transaction fails and the database is left unchanged. An atomic system must guarantee atomicity in each and every situation, including power failures, errors, and crashes.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> A guarantee of atomicity prevents updates to the database from occurring only partially, which can cause greater problems than rejecting the whole series outright. As a consequence, the transaction cannot be observed to be in progress by another database client. At one moment in time, it has not yet happened, and at the next, it has already occurred in whole (or nothing happened if the transaction was cancelled in progress). </p> <div class="mw-heading mw-heading3"><h3 id="Consistency">Consistency</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=3" title="Edit section: Consistency"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Consistency_(database_systems)" title="Consistency (database systems)">Consistency (database systems)</a></div> <p><a href="/wiki/Consistency_(database_systems)" title="Consistency (database systems)">Consistency</a> ensures that a transaction can only bring the database from one consistent state to another, preserving database <a href="/wiki/Invariant_(computer_science)" class="mw-redirect" title="Invariant (computer science)">invariants</a>: any data written to the database must be valid according to all defined rules, including <a href="/wiki/Integrity_constraints" class="mw-redirect" title="Integrity constraints">constraints</a>, <a href="/wiki/Cascading_rollback" class="mw-redirect" title="Cascading rollback">cascades</a>, <a href="/wiki/Database_trigger" title="Database trigger">triggers</a>, and any combination thereof. This prevents database corruption by an illegal transaction. An example of a database invariant is <a href="/wiki/Referential_integrity" title="Referential integrity">referential integrity</a>, which guarantees the <a href="/wiki/Unique_key" title="Unique key">primary key</a>–<a href="/wiki/Foreign_key" title="Foreign key">foreign key</a> relationship.<sup id="cite_ref-Date2012_7-0" class="reference"><a href="#cite_note-Date2012-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Isolation">Isolation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=4" title="Edit section: Isolation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Isolation_(database_systems)" title="Isolation (database systems)">Isolation (database systems)</a></div> <p>Transactions are often executed <a href="/wiki/Concurrent_computing" title="Concurrent computing">concurrently</a> (e.g., multiple transactions reading and writing to a table at the same time). <a href="/wiki/Isolation_(database_systems)" title="Isolation (database systems)">Isolation</a> ensures that concurrent execution of transactions leaves the database in the same state that would have been obtained if the transactions were executed sequentially. Isolation is the main goal of <a href="/wiki/Concurrency_control" title="Concurrency control">concurrency control</a>; depending on the isolation level used, the effects of an incomplete transaction might not be visible to other transactions.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Durability">Durability</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=5" title="Edit section: Durability"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Durability_(database_systems)" title="Durability (database systems)">Durability (database systems)</a></div> <p><a href="/wiki/Durability_(computer_science)" class="mw-redirect" title="Durability (computer science)">Durability</a> guarantees that once a transaction has been committed, it will remain committed even in the case of a system failure (e.g., power outage or <a href="/wiki/Crash_(computing)" title="Crash (computing)">crash</a>). This usually means that completed transactions (or their effects) are recorded in <a href="/wiki/Non-volatile_memory" title="Non-volatile memory">non-volatile memory</a>.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Examples">Examples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=6" title="Edit section: Examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444" /><table class="box-Unreferenced_section plainlinks metadata ambox ambox-content ambox-Unreferenced" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">sources</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/ACID" title="Special:EditPage/ACID">improve this section</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <span class="date-container"><i>(<span class="date">May 2018</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table><p> The following examples further illustrate the ACID properties. In these examples, the database table has two columns, A and B. An <a href="/wiki/Integrity_constraints" class="mw-redirect" title="Integrity constraints">integrity constraint</a> requires that the value in A and the value in B must sum to 100. The following <a href="/wiki/SQL" title="SQL">SQL</a> code creates a table as described above:</p><div class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><pre><span></span><span class="k">CREATE</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">acidtest</span><span class="w"> </span><span class="p">(</span><span class="n">A</span><span class="w"> </span><span class="nb">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="nb">INTEGER</span><span class="p">,</span><span class="w"> </span><span class="k">CHECK</span><span class="w"> </span><span class="p">(</span><span class="n">A</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">B</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">100</span><span class="p">));</span> </pre></div> <div class="mw-heading mw-heading3"><h3 id="Atomicity_2">Atomicity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=7" title="Edit section: Atomicity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>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.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> 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. </p><p>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 <a href="/wiki/Data_consistency" title="Data consistency">consistent state</a>, that is, money is neither debited nor credited if either of those two operations fails.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Consistency_failure">Consistency failure</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=8" title="Edit section: Consistency failure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Consistency is a very general term, which demands that the data must meet all validation rules. In the previous example, the validation is a requirement that <span class="texhtml"><var style="padding-right: 1px;">A</var> + <var style="padding-right: 1px;">B</var> = 100</span>. All validation rules must be checked to ensure consistency. Assume that a transaction attempts to subtract 10 from <var style="padding-right: 1px;">A</var> without altering <var style="padding-right: 1px;">B</var>. Because consistency is checked after each transaction, it is known that <span class="texhtml"><var style="padding-right: 1px;">A</var> + <var style="padding-right: 1px;">B</var> = 100</span> before the transaction begins. If the transaction removes 10 from <var style="padding-right: 1px;">A</var> successfully, atomicity will be achieved. However, a validation check will show that <span class="texhtml"><var style="padding-right: 1px;">A</var> + <var style="padding-right: 1px;">B</var> = 90</span>, which is inconsistent with the rules of the database. The entire transaction must be canceled and the affected rows rolled back to their pre-transaction state. If there had been other constraints, triggers, or cascades, every single change operation would have been checked in the same way as above before the transaction was committed. Similar issues may arise with other constraints. We may have required the data types of both <var style="padding-right: 1px;">A</var> and <var style="padding-right: 1px;">B</var> to be integers. If we were then to enter, say, the value 13.5 for <var style="padding-right: 1px;">A</var>, the transaction will be canceled, or the system may give rise to an alert in the form of a trigger (if/when the trigger has been written to this effect). Another example would be integrity constraints, which would not allow us to delete a row in one table whose primary key is referred to by at least one <a href="/wiki/Foreign_key" title="Foreign key">foreign key</a> in other tables. </p> <div class="mw-heading mw-heading3"><h3 id="Isolation_failure">Isolation failure</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=9" title="Edit section: Isolation failure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>To demonstrate isolation, we assume two transactions execute at the same time, each attempting to modify the same data. One of the two must wait until the other completes in order to maintain isolation. </p><p>Consider two transactions: </p> <ul><li>T<sub>1</sub> transfers 10 from A to B.</li> <li>T<sub>2</sub> transfers 20 from B to A.</li></ul> <p>Combined, there are four actions: </p> <ol><li>T<sub>1</sub> subtracts 10 from A.</li> <li>T<sub>1</sub> adds 10 to B.</li> <li>T<sub>2</sub> subtracts 20 from B.</li> <li>T<sub>2</sub> adds 20 to A.</li></ol> <p>If these operations are performed in order, isolation is maintained, although T<sub>2</sub> must wait. Consider what happens if T<sub>1</sub> fails halfway through. The database eliminates T<sub>1</sub>'s effects, and T<sub>2</sub> sees only valid data. </p><p>By interleaving the transactions, the actual order of actions might be: </p> <ol><li>T<sub>1</sub> subtracts 10 from A.</li> <li>T<sub>2</sub> subtracts 20 from B.</li> <li>T<sub>2</sub> adds 20 to A.</li> <li>T<sub>1</sub> adds 10 to B.</li></ol> <p>Again, consider what happens if T<sub>1</sub> fails while modifying B in Step 4. By the time T<sub>1</sub> fails, T<sub>2</sub> has already modified A; it cannot be restored to the value it had before T<sub>1</sub> without leaving an invalid database. This is known as a <a href="/wiki/Write%E2%80%93write_conflict" title="Write–write conflict">write-write contention</a>,<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> because two transactions attempted to write to the same data field. In a typical system, the problem would be resolved by reverting to the last known good state, canceling the failed transaction T<sub>1</sub>, and restarting the interrupted transaction T<sub>2</sub> from the good state. </p> <div class="mw-heading mw-heading3"><h3 id="Durability_failure">Durability failure</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=10" title="Edit section: Durability failure"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Consider a transaction that transfers 10 from A to B. First, it removes 10 from A, then it adds 10 to B. At this point, the user is told the transaction was a success. However, the changes are still queued in the <a href="/wiki/Disk_buffer" title="Disk buffer">disk buffer</a> waiting to be committed to disk. Power fails and the changes are lost, but the user assumes (understandably) that the changes persist. </p> <div class="mw-heading mw-heading2"><h2 id="Implementation">Implementation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=11" title="Edit section: Implementation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Processing a transaction often requires a sequence of operations that is subject to failure for a number of reasons. For instance, the system may have no room left on its disk drives, or it may have used up its allocated CPU time. There are two popular families of techniques: <a href="/wiki/Write-ahead_logging" title="Write-ahead logging">write-ahead logging</a> and <a href="/wiki/Shadow_paging" title="Shadow paging">shadow paging</a>. In both cases, <a href="/wiki/Lock_(computer_science)" title="Lock (computer science)">locks</a> must be acquired on all information to be updated, and depending on the level of isolation, possibly on all data that may be read as well. In write ahead logging, durability is guaranteed by writing the prospective change to a persistent log before changing the database. That allows the database to return to a consistent state in the event of a crash. In shadowing, updates are applied to a partial copy of the database, and the new copy is activated when the transaction commits. </p> <div class="mw-heading mw-heading3"><h3 id="Locking_vs._multiversioning">Locking vs. multiversioning</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=12" title="Edit section: Locking vs. multiversioning"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many databases rely upon locking to provide ACID capabilities. Locking means that the transaction marks the data that it accesses so that the DBMS knows not to allow other transactions to modify it until the first transaction succeeds or fails. The lock must always be acquired before processing data, including data that is read but not modified. Non-trivial transactions typically require a large number of locks, resulting in substantial overhead as well as blocking other transactions. For example, if user A is running a transaction that has to read a row of data that user B wants to modify, user B must wait until user A's transaction completes. <a href="/wiki/Two-phase_locking" title="Two-phase locking">Two-phase locking</a> is often applied to guarantee full isolation. </p><p>An alternative to locking is <a href="/wiki/Multiversion_concurrency_control" title="Multiversion concurrency control">multiversion concurrency control</a>, in which the database provides each reading transaction the prior, unmodified version of data that is being modified by another active transaction. This allows readers to operate without acquiring locks, i.e., writing transactions do not block reading transactions, and readers do not block writers. Going back to the example, when user A's transaction requests data that user B is modifying, the database provides A with the version of that data that existed when user B started his transaction. User A gets a consistent view of the database even if other users are changing data. One implementation, namely <a href="/wiki/Snapshot_isolation" title="Snapshot isolation">snapshot isolation</a>, relaxes the isolation property. </p> <div class="mw-heading mw-heading3"><h3 id="Distributed_transactions">Distributed transactions</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=13" title="Edit section: Distributed transactions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Distributed_transaction" title="Distributed transaction">Distributed transaction</a></div> <p>Guaranteeing ACID properties in a <a href="/wiki/Distributed_transaction" title="Distributed transaction">distributed transaction</a> across a <a href="/wiki/Distributed_database" title="Distributed database">distributed database</a>, where no single node is responsible for all data affecting a transaction, presents additional complications. Network connections might fail, or one node might successfully complete its part of the transaction and then be required to roll back its changes because of a failure on another node. The <a href="/wiki/Two-phase_commit_protocol" title="Two-phase commit protocol">two-phase commit protocol</a> (not to be confused with <a href="/wiki/Two-phase_locking" title="Two-phase locking">two-phase locking</a>) provides atomicity for <a href="/wiki/Distributed_transaction" title="Distributed transaction">distributed transactions</a> to ensure that each participant in the transaction agrees on whether the transaction should be committed or not.<sup id="cite_ref-Bern2009_13-0" class="reference"><a href="#cite_note-Bern2009-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Briefly, in the first phase, one node (the coordinator) interrogates the other nodes (the participants), and only when all reply that they are prepared does the coordinator, in the second phase, formalize the transaction. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Eventual_consistency" title="Eventual consistency">Eventual consistency</a> (BASE: basically available)</li> <li><a href="/wiki/CAP_theorem" title="CAP theorem">CAP theorem</a></li> <li><a href="/wiki/Concurrency_control" title="Concurrency control">Concurrency control</a></li> <li><a href="/wiki/Java_Transaction_API" class="mw-redirect" title="Java Transaction API">Java Transaction API</a></li> <li><a href="/wiki/Open_Systems_Interconnection" class="mw-redirect" title="Open Systems Interconnection">Open Systems Interconnection</a></li> <li><a href="/wiki/Transactional_NTFS" title="Transactional NTFS">Transactional NTFS</a></li> <li><a href="/wiki/Two-phase_commit_protocol" title="Two-phase commit protocol">Two-phase commit protocol</a></li> <li><a href="/wiki/Create,_read,_update_and_delete" title="Create, read, update and delete">CRUD</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=ACID&action=edit&section=15" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFHaerderReuter1983" class="citation journal cs1"><a href="/wiki/Theo_H%C3%A4rder" title="Theo Härder">Haerder, T.</a>; <a href="/wiki/Andreas_Reuter" title="Andreas Reuter">Reuter, A.</a> (1983). "Principles of transaction-oriented database recovery". <i>ACM Computing Surveys</i>. <b>15</b> (4): 287. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1145%2F289.291">10.1145/289.291</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:207235758">207235758</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=ACM+Computing+Surveys&rft.atitle=Principles+of+transaction-oriented+database+recovery&rft.volume=15&rft.issue=4&rft.pages=287&rft.date=1983&rft_id=info%3Adoi%2F10.1145%2F289.291&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A207235758%23id-name%3DS2CID&rft.aulast=Haerder&rft.aufirst=T.&rft.au=Reuter%2C+A.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AACID" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGray1981" class="citation conference cs1"><a href="/wiki/Jim_Gray_(computer_scientist)" title="Jim Gray (computer scientist)">Gray, Jim</a> (September 1981). <a rel="nofollow" class="external text" href="http://research.microsoft.com/~gray/papers/theTransactionConcept.pdf">"The Transaction Concept: Virtues and Limitations"</a> <span class="cs1-format">(PDF)</span>. <i>Proceedings of the 7th International Conference on Very Large Databases</i>. Cupertino, California: <a href="/wiki/Tandem_Computers" title="Tandem Computers">Tandem Computers</a>. pp. <span class="nowrap">144–</span>154<span class="reference-accessdate">. Retrieved <span class="nowrap">March 27,</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.atitle=The+Transaction+Concept%3A+Virtues+and+Limitations&rft.btitle=Proceedings+of+the+7th+International+Conference+on+Very+Large+Databases&rft.place=Cupertino%2C+California&rft.pages=%3Cspan+class%3D%22nowrap%22%3E144-%3C%2Fspan%3E154&rft.pub=Tandem+Computers&rft.date=1981-09&rft.aulast=Gray&rft.aufirst=Jim&rft_id=http%3A%2F%2Fresearch.microsoft.com%2F~gray%2Fpapers%2FtheTransactionConcept.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AACID" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGrayReuter1993" class="citation book cs1"><a href="/wiki/Jim_Gray_(computer_scientist)" title="Jim Gray (computer scientist)">Gray, Jim</a>; <a href="/wiki/Andreas_Reuter" title="Andreas Reuter">Reuter, Andreas</a> (1993). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/transactionproce0000gray"><i>Distributed Transaction Processing: Concepts and Techniques</i></a></span>. <a href="/wiki/Morgan_Kaufmann" class="mw-redirect" title="Morgan Kaufmann">Morgan Kaufmann</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/1-55860-190-2" title="Special:BookSources/1-55860-190-2"><bdi>1-55860-190-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Distributed+Transaction+Processing%3A+Concepts+and+Techniques&rft.pub=Morgan+Kaufmann&rft.date=1993&rft.isbn=1-55860-190-2&rft.aulast=Gray&rft.aufirst=Jim&rft.au=Reuter%2C+Andreas&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Ftransactionproce0000gray&rfr_id=info%3Asid%2Fen.wikipedia.org%3AACID" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://aws.amazon.com/compare/the-difference-between-acid-and-base-database/">"ACID vs BASE Databases - Difference Between Databases - AWS"</a>. <i>Amazon Web Services, Inc</i><span class="reference-accessdate">. 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Retrieved <span class="nowrap">2011-03-23</span></span>. <q>An operation during which a processor can simultaneously read a location and write it in the same bus operation. This prevents any other processor or I/O device from writing or reading memory until the operation is complete.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=webopedia.com&rft.atitle=Atomic+operation&rft.date=2003-11-25&rft_id=http%3A%2F%2Fwww.webopedia.com%2FTERM%2FA%2Fatomic_operation.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AACID" class="Z3988"></span></span> </li> <li id="cite_note-Date2012-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-Date2012_7-0">^</a></b></span> <span class="reference-text">C. J. 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New York: McGraw-Hill. p. 631. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-07-352332-3" title="Special:BookSources/978-0-07-352332-3"><bdi>978-0-07-352332-3</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/436031093">436031093</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Transactions&rft.btitle=Database+system+concepts&rft.place=New+York&rft.pages=631&rft.edition=6th&rft.pub=McGraw-Hill&rft.date=2011&rft_id=info%3Aoclcnum%2F436031093&rft.isbn=978-0-07-352332-3&rft.aulast=Silberschatz&rft.aufirst=Abraham&rft.au=Korth%2C+Henry+F.&rft.au=Sudarshan%2C+S.&rft_id=https%3A%2F%2Fwww.worldcat.org%2Ftitle%2F436031093&rfr_id=info%3Asid%2Fen.wikipedia.org%3AACID" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.oracle.com/cd/E17276_01/html/programmer_reference/transapp_atomicity.html">"Atomicity"</a>. <i>docs.oracle.com</i><span class="reference-accessdate">. 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Archived from <a rel="nofollow" class="external text" href="http://www.elsevierdirect.com/product.jsp?isbn=9781558606234">the original</a> on 2010-08-07.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Chapter+8&rft.btitle=Principles+of+Transaction+Processing&rft.edition=2nd&rft.pub=Morgan+Kaufmann+%28Elsevier%29&rft.date=2009&rft.isbn=978-1-55860-623-4&rft.aulast=Bernstein&rft.aufirst=Philip+A.&rft.au=Newcomer%2C+Eric&rft_id=http%3A%2F%2Fwww.elsevierdirect.com%2Fproduct.jsp%3Fisbn%3D9781558606234&rfr_id=info%3Asid%2Fen.wikipedia.org%3AACID" class="Z3988"></span></span> </li> </ol></div></div> <div style="clear:both;" class=""></div> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist 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