Step 1. If the standby database is in managed recovery mode, it will need to be cancelled and the instance shutdown using the IMMEDIATE option:

SQL> recover managed standby database cancel;
Media recovery complete.

SQL> shutdown immediate
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Step 2. Startup the instance and then MOUNT the DB in standby mode:

SQL> connect / as sysdba
Connected to an idle instance.

SQL> startup nomount

SQL> alter database mount standby database;

Database altered.

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Step3. Apply the primary database’s archived logs by recovering the standby database:

SQL> recover standby database until cancel;

A CANCEL will need to be performed as this is Incomplete Recovery.

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Step4. Activate the standby database.

In issuing the ALTER DATABASE ACTIVATE STANDBY DATABASE command, the standby bit in the control file is reset. This process takes the database back to nomount mode:

SQL> alter database activate standby database;

Database altered.

NOTE: This process can take several minutes to complete so be patient!

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Step 7. Shutdown and restart the new primary database. This step ensures that all file headers are reset and clears all buffers.

SQL> shutdown immediate

SQL> startup open

SQL>select name,open_mode,database_role from v$database;

8. Check Listener

9.Try to connect “sqlplus username/passwd@pr1