How to switch primary database into a standby database and a standby database into a primary database :

 - Switching the primary and standby databases:

- set oracle_sid=primarydb_name

- sqlplus / as sysdba

- alter database commit to switchover to PHYSICAL STANDBY WITH SESSION SHUTDOWN;

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- Connect to standby database 'standbydb_name' and run the following command :

- alter database commit to switchover to primary;

- select database_role from v$database;

- alter database open;