This illustration shows a typical two-site Data Guard configuration after a switchover operation has occurred. In the switch.gif figure, the San Francisco site (which was originally the primary site) is now operating as the standby site and the Boston site is now operating as the primary site.

On the left-hand side of the figure, a terminal running an application that was previously sending its read/write transactions to the San Francisco site is now sending its transactions to the Boston site.

On the new primary site in Boston, the figure shows the online redo logs and local archived redo logs being generated and archived through Oracle Net to the standby site in San Francisco.