High availability has become a critical requirement for virtually every industry in the business world today. A computer system failure can result in the failure of a business to operate, and every minute of down time can mean lost revenue, productivity, and profit.

For systems to achieve continuous operations, the system components (hardware, operating system, middleware, and applications) must be implemented in a fashion where failures are transparent to the end user. In addition, mechanisms must be in place to allow system maintenance without disrupting the current workload