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Step 1 Determine the SCN to which to flash back the failed primary database.

On the new primary database, issue the following query to determine the SCN to which you want to flash back the failed primary database:

SQL> SELECT APPLIED_SCN AS FLASHBACK_SCN FROM V$LOGSTDBY_PROGRESS;

Step 2 Determine the log files that must be copied to the failed primary database for Flashback Database.

On the new primary database, issue the following query to determine the log files that must be copied to the failed primary database for Flashback Database to reach a consistent state

SQL> SELECT NAME FROM DBA_LOGSDTBY_LOG  2>   WHERE NEXT_CHANGE# >   3>           (SELECT VALUE FROM DBA_LOGSTDBY_PARAMETERS  4>   WHERE NAME = 'STANDBY_BECAME_PRIMARY_SCN') 5>           AND FIRST_CHANGE 

Step 3 Flash back the failed primary database.
To create a new logical standby database, shut down the database (if necessary), mount the failed primary database, flash it back to the FLASHBACK_SCN determined in step 1, and enable the database guard.
SQL> SHUTDOWN IMMEDIATE; SQL> STARTUP MOUNT; SQL> FLASHBACK DATABASE TO SCN became_primary_scn; SQL> ALTER DATABASE GUARD ALL;

Step 4 Open the database with the RESETLOGS option.
SQL> ALTER DATABASE OPEN RESETLOGS;

Step 5 Create a database link to the new primary database and start SQL Apply.
SQL> CREATE PUBLIC DATABASE LINK mylink 2> CONNECT TO system IDENTIFIED BY password    3> USING 'service_name_of_new_primary_database';  SQL> ALTER DATABASE START LOGICAL STANDBY APPLY NEW PRIMARY mylink; 
The role reversal is now complete.