Oracle7 Server Distributed Systems Volume II: Replicated Data
Survivability
The Oracle symmetric replication facility also supports system survivability. Two sites maintaining replicated master tables can serve as fail-over sites for each other. If one site fails, processing can continue on the surviving site against the data that has been replicated from the failed system. When the failed system is restored, its database can be re-instantiated from the failover site, or conflict detection/resolution technology can be employed to re-establish consistency between the two databases. Symmetric replication, therefore, adds another option for system fault tolerance.
The Oracle Parallel Server provides system fault tolerance in locally connected cluster or massively parallel environments. In these environments, the Parallel Server will usually be the preferred option. Symmetric replication extends Oracle's system fault tolerance capability to geographically separated systems and local non-clustered environments. Another option is a standby database configuration which can offer performance advantages while also providing protection across geographically separated systems.