To use the RAC failover feature, you must be using Oracle 10g or later.
Oracle provides technology called Real Application Clusters (RAC), which allows an Oracle database to run in a clustered environment; in other words, the database can be serviced by several Oracle instances spread across several host machines. In this clustered environment, a “virtual instance” directs and redirects instance connections from one instance to another when failover occurs. If an instance fails, the client fails over to a secondary instance in the RAC environment. ECDA Option for Oracle uses the Oracle feature called Transparent Application Failover (TAF) to provide this failover function.
When a heterogeneous environment includes an Oracle RAC environment, ECDA Option for Oracle support of TAF helps prevent an outage due to an Oracle instance failure, thus reducing operational downtime.
In support of Oracle RAC, ECDA Option for Oracle manages the failover from one instance to another as follows:
It connects to an Oracle database instance that is in an Oracle RAC environment.
When failure occurs, it sends the ECDA Option for Oracle client connection to alternate Oracle instances that are defined in the ECDA Option for Oracle tnsnames.ora file.
It reports any error messages resulting from a failover to the client application.
If all backup instances are unavailable, an ORA-03113
error is returned to the client application.
