Database Reference
In-Depth Information
The whole failover operation does not take long. The good news is that the operation did not involve data loss.
The old primary database's alert.log reports:
Data Guard Broker: Beginning failover
ALTER DATABASE FAILOVER TO CDBFSDCB
[...log information about database recovery]
Terminal Recovery finished with No-Data-Loss
2013-09-16 12:05:57.922000 +01:00
Incomplete Recovery applied until change 1870588 time 09/16/2013 11:57:20
Media Recovery Complete (CDBFSDCB)
Terminal Recovery: successful completion
As part of the failover operation the protection mode is automatically downgraded, which is reflected in the
output of the “show configuration” command.
DGMGRL> show configuration
Configuration - fsconfig
Protection Mode: MaxAvailability
Databases:
CDBFSDCB - Primary database
Warning: ORA-16629: database reports a different protection level from the protection mode
CDBFSDCA - Physical standby database (disabled)
ORA-16661: the standby database needs to be reinstated
Fast-Start Failover: DISABLED
Configuration Status:
WARNING
Two tasks are now remaining. The message that the database reports a different protection level from the
protection mode refers to V$DATABASE.PROTECTION_MODE and PROTECTION_LEVEL. They are not identical
since there is a network connectivity problem between the databases. Additionally the old primary database will not
currently accept archived logs from the new primary: it still thinks it is the primary. Proceed with the reinstation of the
failed primary.
Reinstating the old primary database
A failover operation always required a complete rebuild of the failed database up to Oracle 10g. Luckily this has
changed with the introduction of the Flashback Database command. In addition to the recreation of the failed
standby which still might be required you have the option to reinstate the failed database. Reinstating the database is
a lot quicker than a recreation: it simply flashes the database back to the SCN before the standby became a primary
(as per V$DATABASE.STANDBY_BECAME_PRIMARY_SCN on the old primary), and converts it to a standby database. If such
an operation is possible the Broker will report the following message when you query the configuration status:
CDBFSDCA - Physical standby database (disabled)
ORA-16661: the standby database needs to be reinstated
 
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