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• In all cases, after a failover, the original primary database can no longer participate in the Data Guard configuration.

• In most cases, other logical or physical standby databases not directly participating in the failover remain in the configuration and do not have to be shut down or restarted.

• In some cases, it might be necessary to re-create all standby databases after configuring the new primary database.

sql> SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;
THREAD#    LOW_SEQUENCE# HIGH_SEQUENCE#
---------- ------------- --------------
         1            90             92

In the result : 
SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE 'filespec1';

Step 2 
Repeat step 1 until all gaps resolved

Step 3 
Coping any other missing archive redo logs
For ex:
SQL> SELECT UNIQUE THREAD# AS THREAD, MAX(SEQUENCE#)
  2> OVER (PARTITION BY thread#) AS LAST from V$ARCHIVED_LOG;

    THREAD       LAST
---------- ----------
         1        100

SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE 'filespec1';

Step 4 Initiate a failover on the target physical standby database

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH FORCE;

Step 5 Convert physical standby database to primary database role.

SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;

Step 6 Finish the transition of the standby database to primary database role.

 6.1 If the physical standby database have not been opened in read_only mode since last time it is started ,
     issue the SQL alter database open to open the new primary database:
     
     SQL> ALTER DATABASE OPEN;

6.2 If the physical stantdby database have been opend in read_only mode since last time it is started ,you must shut down the target 
    database and restarted it ;
  
    SQL> SHUTDOWN IMMEDIATE;
    SQL> STARTUP;