A standby database environment can provide protection against planned and unplanned downtime as well as against data loss in case the primary database environment becomes unavailable. With the use of proper technology, it is also possible keep the standby database synchronized with the primary database, thereby providing almost transparent continued database operations even in the face of problems ranging from user errors to system failures, to disasters. A standby database has therefore always been a key to high availability and protection for any important production system.
Snapshot Standby – The snapshot standby database is an updatable standby database that provides full data protection for the primary database. It continues to receive redo data from the primary but the apply process is halted while the standby database is open for read/write for test. When testing is complete, a single command reverts the standby database back to its original state, discarding the changes made while it was open read-write and applying the accumulated redo logs to make it current with the primary database.