Editing ACID (section)

=== Distributed transactions ===
{{Main article|Distributed transaction}}
Guaranteeing ACID properties in a [[distributed transaction]] across a [[distributed database]], 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 [[two-phase commit protocol]] (not to be confused with [[two-phase locking]]) provides atomicity for [[distributed transaction]]s to ensure that each participant in the transaction agrees on whether the transaction should be committed or not.<ref name=Bern2009>{{cite book |author-link1=Phil Bernstein |first1=Philip A. |last1=Bernstein |first2=Eric |last2=Newcomer |date=2009 |url=http://www.elsevierdirect.com/product.jsp?isbn=9781558606234 |title=Principles of Transaction Processing |edition=2nd |archive-url=https://web.archive.org/web/20100807151625/http://www.elsevierdirect.com/product.jsp?isbn=9781558606234 |archive-date=2010-08-07 |chapter=Chapter 8 |publisher=Morgan Kaufmann (Elsevier) |isbn=978-1-55860-623-4}}</ref> 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.