Active Data Guard

In the database has been started in SQL*Plus using STARTUP MOUNT and the database is subsequently opened read only, then invoking managed recovery will enable Active Data Guard. For example:

[oracle@server14]$ sqlplus / as sysdba
SQL> STARTUP MOUNT
ORACLE instance started.
Total System Global Area 6497189888 bytes
Fixed Size 2238672 bytes
Variable Size 3372222256 bytes
Database Buffers 3103784960 bytes
Redo Buffers 18944000 bytes
Database mounted
Database opened

SQL> SELECT database_role, open_mode FROM v$database;

DATABASE_ROLE    OPEN_MODE
---------------- --------------------
PHYSICAL STANDBY MOUNTED

SQL> ALTER DATABASE OPEN READ ONLY;

SQL> SELECT database_role, open_mode FROM v$database;

DATABASE_ROLE    OPEN_MODE
---------------- --------------------
PHYSICAL STANDBY READ ONLY

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE
USING CURRENT LOGFILE
WITH SESSION SHUTDOWN;

SQL> SELECT database_role, open_mode FROM v$database;

DATABASE_ROLE    OPEN_MODE
---------------- --------------------
PHYSICAL STANDBY READ ONLY WITH APPLY