IT disaster recovery (also, simply disaster recovery (DR)) is the process of maintaining or reestablishing vital infrastructure and systems following a natural or human-induced disaster, such as a storm or battle. DR employs policies, tools, and procedures with a focus on IT systems supporting critical business functions.[1] This involves keeping all essential aspects of a business functioning despite significant disruptive events; it can therefore be considered a subset of business continuity (BC).[2][3] DR assumes that the primary site is not immediately recoverable and restores data and services to a secondary site.