Inaccessible Log File This parameter, disabled by default, allows for failover to be initiated in the event that LGWR is unable to write to a member of a log group.Corrupted Controlfile Enabled by default, the detection of controlfile corruption will result in immediate failover.Corrupted Dictionary Failover is initiated if corruption of a critical database object is found.Datafile Offline Failover is initiated if a datafile on the primary database experiences an I/O error resulting in a datafile being taken offline.When one of the following user configurable conditions are met, the broker will bypass the FastStartFailoverThreshold, immediately initiating failover: Oracle 11 g introduced user-configurable failover conditions. Note that Fast-Start Failover will not be initiated when a database is shut down using normal, transactional, or immediate options. Under this circumstance for failover, the Oracle Data Guard Broker will attempt to reinstate the failed primary database as a standby when connectivity is re-established. Should it detect that the primary database (all instances in an Oracle RAC environment) has become unavailable or a connection with the primary database is not able to be made, it will issue a failover after waiting the number of seconds specified by the FastStartFailoverThreshold property. The Observer is a component of the DGMGRL interface that is configured on a system outside the systems actually running the Oracle Data Guard configuration, which monitors the availability of the primary database. The key to this feature is a monitoring process appropriately named the Observer. Fast-Start Failover enables the broker to perform these tasks automatically in the same time that it would typically take a DBA to log into the system. At best, we are looking at a 15 minute outage-that is, if a DBA is on site, monitoring every move of the standby. At that point, the DBA must log into the system and execute the required commands to failover the database and if possible reinstate that failed primary as a standby. Let’s consider what happens in a typical failover scenario: First, the DBA will receive a notification that the primary database has failed. This feature increases the availability of the database by eliminating the need for DBA involvement as part of the failover process. Fast-Start Failover is a feature that allows the Oracle Data Guard broker to failover a failed primary database automatically to a predetermined standby database.
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