The following sections explain how Data Guard manages the transmission of redo data, the application of redo data, and changes to the database roles:

1.Redo Transport Services: Control the automated transfer of redo data from the production database to one or more archival destinations.

2.Log Apply Services: Apply redo data on the standby database to maintain transactional synchronization with the primary database. Redo data can be applied either from archived redo log files, or, if real-time apply is enabled, directly from the standby redo log files as they are being filled, without requiring the redo data to be archived first at the standby database.

3.Role Transitions: Change the role of a database from a standby database to a primary database, or from a primary database to a standby database using either a switchover or a failover operation.