As information increasingly becomes the lifeblood of business, the databases that store business critical information become vital to business operation, with downtime for the DBMS creating critical productivity and opportunity impacts on the company’s business. With the move to deploy both new and old applications on the web, this dependency on DBMS availability escalates as the increased access to

information causes more databases to become mission critical. The heightened availability requirements have forced open systems databases to provide the types of HA once reserved for mainframe environments.

The nature of databases complicates HA because it must be achieved in a way that maintains the consistency of the data in the database.