The initial configuration:

DGMGRL> show configuration

Configuration - myconf

  Protection Mode: MaxPerformance
  Databases:
    prima - Primary database
    physt - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

The version is still 11.2.0.1 like in the previous posting. I will now failover to physt while prima keeps running. Attention: If there is a productive service started on the NEW Primary, make sure to stop it. Else new productive connections will access the NEW Primary! We will deliberately cause a Split Brain situation here with two Primary Databases. This may cause problems in a productive environment and is not recommended.

DGMGRL> failover to physt;
Performing failover NOW, please wait...
Error: ORA-16600: not connected to target standby database for failover

Failed.
Unable to failover
DGMGRL> exit
[oracle@uhesse ~]$ dgmgrl sys/oracle@physt
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> failover to physt;
Performing failover NOW, please wait...
Failover succeeded, new primary is "physt"

The error above shows that we cannot failover, connected to the (still working) Primary but must connect to the Standby first. Now there are two Primary Databases:

[oracle@uhesse ~]$ sqlplus sys/oracle@physt as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Mon Jan 16 10:25:51 2012

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> select database_role from v$database;

DATABASE_ROLE
----------------
PRIMARY

SQL> connect sys/oracle@prima as sysdba
Connected.
SQL> select database_role from v$database;

DATABASE_ROLE
----------------
PRIMARY

I want to make the NEW Primary a Standby again. Similar to a Reinstate, that needs Flashback Logs. My two Databases generate Flashback Logs, so that requirement is met.

SQL> connect sys/oracle@physt as sysdba
Connected.
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area  313159680 bytes
Fixed Size            2212936 bytes
Variable Size          264244152 bytes
Database Buffers       41943040 bytes
Redo Buffers            4759552 bytes
Database mounted.
SQL> flashback database to before resetlogs;

Flashback complete.

SQL> alter database convert to physical standby;

Database altered.

This modified the controlfile and puts the Instance in NOMOUNT. We need to restart into MOUNT:

SQL> shutdown immediate
ORA-01507: database not mounted

ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area  313159680 bytes
Fixed Size            2212936 bytes
Variable Size          264244152 bytes
Database Buffers       41943040 bytes
Redo Buffers            4759552 bytes
Database mounted.
SQL> recover managed standby database using current logfile disconnect;
Media recovery complete.
SQL> select status,sequence# from v$managed_standby where process='MRP0';

STATUS          SEQUENCE#
------------ ----------
WAIT_FOR_LOG         12

We want to see here APPLYING LOG – the redo is not yet transmitted from the OLD Primary.

SQL> connect sys/oracle@prima as sysdba
Connected.
SQL> select sequence# from v$log where status='CURRENT';

 SEQUENCE#
----------
    13

SQL> alter system set log_archive_dest_2='service=physt db_unique_name=physt';

System altered.

SQL> alter system set log_archive_dest_state_2=enable;

System altered.

SQL> alter system switch logfile;

System altered.

SQL> connect sys/oracle@physt as sysdba
Connected.
SQL> select status,sequence# from v$managed_standby where process='MRP0';

STATUS          SEQUENCE#
------------ ----------
APPLYING_LOG         15

Everything is fine now on the Database Layer: OLD Primary is still Primary, NEW Primary is again Standby, applying Redo from the OLD Primary. Only the Data Guard Broker is confused now – we need to create a new configuration:

[oracle@uhesse ~]$ dgmgrl sys/oracle@prima
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> show configuration;
ORA-16795: the standby database needs to be re-created

Configuration details cannot be determined by DGMGRL
[oracle@uhesse ~]$ sqlplus sys/oracle@physt as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Mon Jan 16 10:46:13 2012

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> alter system set dg_broker_start=false;

System altered.

SQL> connect sys/oracle@prima as sysdba
Connected.
SQL> alter system set dg_broker_start=false;

System altered.

SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@uhesse ~]$ rm $ORACLE_HOME/dbs/dr*

The above deleted the Broker Config Files. Now we create a new Broker Configuration:

[oracle@uhesse ~]$ sqlplus sys/oracle@physt as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Mon Jan 16 10:48:22 2012

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> alter system set dg_broker_start=true;

System altered.

SQL> connect sys/oracle@prima as sysdba
Connected.
SQL> alter system set dg_broker_start=true;

System altered.

[oracle@uhesse ~]$ dgmgrl sys/oracle@prima
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> create configuration mycon as primary database is prima connect identifier is prima;
Configuration "mycon" created with primary database "prima"
DGMGRL> add database physt as connect identifier is physt maintained as physical;
Database "physt" added
DGMGRL> enable configuration;
Enabled.
DGMGRL> show configuration;

Configuration - mycon

  Protection Mode: MaxPerformance
  Databases:
    prima - Primary database
    physt - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

That was it