Steps for Database Failover

Check the archive log sync gap in DR if we found gap we need to sync. Check the gap by using bellow query .

1. select name,open_mode from v$database;

2. select name,open_mode,database_role from v$database;

3.SELECT ARCH.THREAD# "Thread", ARCH.SEQUENCE# "Last Sequence Received", APPL.SEQUENCE#"Last Sequence Applied", (ARCH.SEQUENCE# - APPL.SEQUENCE#) "Difference"
FROM
(SELECT THREAD# ,SEQUENCE# FROM V$ARCHIVED_LOG WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$ARCHIVED_LOG GROUP BY THREAD#)) ARCH,
(SELECT THREAD# ,SEQUENCE# FROM V$LOG_HISTORY WHERE (THREAD#,FIRST_TIME ) IN (SELECT THREAD#,MAX(FIRST_TIME) FROM V$LOG_HISTORY GROUP BY THREAD#)) APPL
WHERE
ARCH.THREAD# = APPL.THREAD#

4. ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;

5. select name,open_mode,database_role from v$database;

6. ALTER DATABASE ACTIVATE STANDBY DATABASE;

7. select name,open_mode,database_role from v$database;

8. alter database open;

9. select name,open_mode,database_role from v$database;

10.Shut immediate;

11. Startup;