step by step Oracle 12c Data Guard Failover

 Step:1 In standby database check the database role and open_mode

SQL> SELECT OPEN_MODE,PROTECTION_MODE,DATABASE_ROLE FROM V$DATABASE;

OPEN_MODE         PROTECTION_MODE      DATABASE_ROLE
-------------------- -------------------- ----------------
READ ONLY WITH APPLY MAXIMUM PERFORMANCE  PHYSICAL STANDBY

  Step:2 Check archive log gap sequence

 SQL> SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;

no rows selected

 Step:3 Cancel MRP process in standby database

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

Database altered. 

 Step:4 Bring up standby database as primary 

SQL> alter database recover managed standby database finish;

Database altered.

SQL> alter database activate standby database;

Database altered.

Managed recovery process has been stopped between primary and standby database and standby becomes primary database.

Step:5 Shutdown and startup database and verify database name its open mode and its role.

SQL> shutdown immediate
ORA-01109: database not open


Database dismounted.
ORACLE instance shut down.

SQL> startup
ORA-32004: obsolete or deprecated parameter(s) specified for RDBMS instance
ORACLE instance started.

Total System Global Area 1.6106E+11 bytes
Fixed Size            7653336 bytes
Variable Size         8.1604E+10 bytes
Database Buffers     7.8920E+10 bytes
Redo Buffers          529215488 bytes
Database mounted.
Database opened.
SQL> select open_mode,database_role from v$database;

OPEN_MODE         DATABASE_ROLE
-------------------- ----------------
READ WRITE         PRIMARY