There are two services that we need to check for the verification of the logical standby configuration, which are the redo transport service and the SQL Apply service. There are several ways to check the status of these services. You can use alert log and trace files (whenever necessary) or you can query the views of the logical standby database that contains information about the status of the Data Guard services. Another way for controlling is modifying the primary database tables and querying the same tables on the logical standby. We'll now query the most useful views to gather information about the configuration and service status.