Request_Only Mode for Data Guard

Demonstrates a how replication request_only mode supports Data Guard.

The purpose of the request_only mode is to allow a recovery appliance to request backups from the second Recovery Appliance of a pair, in order to fill gaps in its backups, such as after an offline period. There is no active replication between the upstream and downstream. Replication only happens when backups are requested by the upstream RA-x to fill gaps after an outage. Data Guard and redo logs keeps the remote database in sync with the local database.

Figure 15-3 shows two data centers for local and remote, where the primary site is local RA-x and the standby site is remote RA-y. Backups are taken at primary and standby databases, each to their respective local Recovery Appliances. In request_only mode, replication traffic does not occur from RA-x to RA-y. Dataguard and redo logs keeps the remote database in sync with the local database.

The replication servers are configured for bi-direction replication. When using add_replication_server, RA-y gets a protection policy as normal. However, add_replication_server for RA-x has the protection policy with REQUEST_ONLY=TRUE.

When a switchover from the primary (local) to the secondary (remote) has happened, replication traffic does not occur from RA-x to RA-y. However, the RA-x catalog is kept in sync with the RA-y backups. When RA-x is offline, standby backups continue to be sent to RA-y with full recoverability to both data centers. When RA-x comes back online, RA-x requests missing backups from RA-y in order to sync with the current state.

Figure 15-3 Replication Request Mode of Backup Anywhere

Description of "Figure 15-3 Replication Request Mode of Backup Anywhere"