For active dataguard:-

Create physical standby by following my post How to Create Physical Standby and then on Standby execute following:-

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE OPEN READ ONLY;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

That’s it, Now you can see that your physical standby is in read only mode, as promised by the Active DataGuard feature.

select name, open_mode, database_role from v$database;