Data Guard Maximum Availability Mode Tips Oracle Tips by Burleson Consulting December 9, 2011

MAXIMUM AVAILABILITY protection mode

MAXIMUM AVAILABILITY is another ‘no-data-loss’ protection mode. It can be argued that it can be placed somewhere between the ‘no-data-loss’ and ‘minimal-data-loss’ category.

The setup of maximum availability protection is the same as maximum protection. In MAXIMUM AVAILABILITY mode, the primary database does not halt if it cannot transmit redo data to at least one participating standby database.

During this period the protection mode is switched to MAXIMUM PERFORMANCE, the lowest level of data protection.

When Data Guard is in MAXIMUM PERFORMANCE mode, data can potentially be lost if the primary database crashes and the redo logs have not been transferred to any archival destination.

The protection mode is upgraded to MAXIMUM AVAILABILITY on next log switch if the log transfer service has resumed transmission of the redo data to at least one Oracle instance participating in maximum availability configuration and all the archive gap sequences have been resolved.

A logical Oracle instance can also participate in MAXIMUM AVAILABILITY mode. Only the availability of the primary database is enhanced in this mode.  The performance issues are the same as for MAXIMUM PROTECTION mode. The following statement should be executed on the primary database to put it in a maximum availability Data Guard configuration. The primary database should be mounted but not open to execute this statement:

ALTER DATABASE SET Oracle instance TO MAXIMIZE AVAILABILITY;