Dataguard : Activating Standby (Failover) when Primary is Down

In this post, I will show you how easy it is to fail-over on standby dataguard database when primary is not available.

sys@ PRIMARY> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            C:\app\product\11.2.0\dbhome_1\oradata
Oldest online log sequence     207
Next log sequence to archive   209
Current log sequence           209

sys@ SECONDARY> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     207
Next log sequence to archive   0
Current log sequence           209

DGMGRL> connect sys/manager@secondary
Connected.
DGMGRL> startup mount;
ORACLE instance started.
Database mounted.

DGMGRL> connect sys/manager@primary
Connected.
DGMGRL> shutdown abort;
ORACLE instance shut down.

DGMGRL> switchover to ‘secondary’;
Performing switchover NOW, please wait…
Error: ORA-01034: ORACLE not available
Error: ORA-16625: cannot reach database “primary”
Failed.
Unable to switchover, primary database is still “primary”

DGMGRL> connect sys/manager@secondary
Connected.
DGMGRL> failover to secondary;
Performing failover NOW, please wait…
Failover succeeded, new primary is “secondary”
DGMGRL> show configuration;
Configuration – sample
Protection Mode: MaxPerformance
Databases:
secondary – Primary database
primary   – Physical standby database (disabled)
ORA-16661: the standby database needs to be reinstated
fast-Start Failover: DISABLED
Configuration Status: SUCCESS

Please note Secondary which is now a PRIMARY Database , it’s ARCHIVE log sequence is reset to 1

sys@ SECONDARY> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     1
Next log sequence to archive   1
Current log sequence           1

If you try and start Primary database (failed over) it won’t be opened by dgmgrl , alrtlog should have following error message

Data Guard: version check completed
Data Guard determines a failover has occurred – this is no longer a primary database
ORA-16649 signalled during: alter database open…