oracle data guard is maximum availiblity solution which maintain physical standby databases and in case of failure of production can switch production role to and standby database.
Oracle Data Guard is the most effective and comprehensive data availability, data protection, and disaster recovery solution for enterprise databases. It provides the management, monitoring, and automation software infrastructure to create and maintain one or more synchronized standby databases to protect data from failures, disasters, errors, and corruptions. Data Guard standby databases can be located at remote disaster recovery sites thousands of miles away from the production data center, or they may be located in the same city, same campus, or even in the same building. If the production database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch any standby database to the production role, thus minimizing downtime and preventing any data loss.