This illustration shows a two-site Data Guard configuration that is in the process of a switchover operation. In this illustration, the San Francisco site (which was originally the primary site) has changed to the standby role, but the Boston site has not yet changed to the primary role. At this point in time, both the San Francisco and Boston sites are operating in the standby role.

Applications that were previously sending read/write transactions to the San Francisco site are preparing to send read/write transactions to the Boston site. On the Boston standby site, the standby database online redo logs and local archived redo logs are still being generated. However, no redo logs are being sent or received over the Oracle Net network. This figure shows that both of the standby sites are capable of operating in read-only mode.