Question: How to identify if Active Data Guard (ADG) is enabled on a Standby database?

The concept of an Active Data Guard, also known as Real-Time Query, is when it allows read-only access on the Physical standby node at the same time as applying archived transactions from the Primary node.

For that to happen, the Standby database must be open in READ ONLY mode *and* the MRP (the apply process) started.

There are 2 ways to verify if ADG is enabled:

1. check the alert.log if the Standby database is opened in READ ONLY mode and if the MRP process is started:

Below sql will start the MRP process:

SQL>ALTER DATABASE RECOVER MANAGED STANDBY DATABASE [ options ];

OR

2. run the following query on the Standby database, for example:

SQL> select open_mode, controlfile_type from v$database;

OPEN_MODE                       CONTROLFILE
----------------------------------------------
READ ONLY WITH APPLY            STANDBY