This figure shows an Oracle Clusterware and Oracle Data Guard architecture that consists of a primary and a secondary site. At the top of the figure are three clients sending requests through the WAN traffic manager to several application servers on the primary site.
On the left side of the figure, the primary site contains an Oracle application server, two database nodes (active and passive), and an Oracle database. The secondary site on the right side of the figure contains a similar configuration, but the application servers are connected to the WAN traffic manager by a dotted line to indicate that they are not actively processing client requests at this time. A dedicated network connects the primary site and the standby site. An arrow pointing from the primary site to the standby site indicates that Oracle Data Guard is transmitting redo data from the primary database to the standby to keep the standby database synchronized transactionally. Another line goes from the primary site application servers to the active node on the standby site to indicate that real-time queries are occurring.
Oracle Clusterware is not shown in the figure because the Oracle Clusterware software transparently enables servers to operate as one server and manages the availability of user applications and Oracle databases.