Data Guard guaranteed instance protection mode Tips Oracle Database Tips by Donald BurlesonDecember 9, 2015

Oracle Data Guard - Guaranteed Instance Protection Mode

ALTER DATABASE SET STANDBY DATABASE PROTECTED;

This protection mode offers a 'no-data-loss' environment with enhanced availability of the primary database. The primary database will not shut down if it cannot transmit redo data to the participating standby database.  Instead, the data on the primary database will temporarily diverge from the standby database. During this period, the protection mode is lowered to the Rapid Protection mode.

Once the connectivity to a Oracle instance is reestablished, the archived redo logs are transmitted to the standby site. It can be argued that some data may be lost in this mode if the primary database crashes when the Oracle instance has been lowered to the rapid protection mode.  In addition, un-archived redo logs could be lost during the primary database crash.

instance Protection Mode

The log_archive_dest_n parameter settings and standby redo log requirements are the same as the one for guaranteed protection mode. The failure resolution policy is unprotected which allows data divergence when the last participating Oracle instance is unreachable for archiving. The following statement can be used to set the failure resolution policy:

ALTER DATABASE SET Oracle instance UNPROTECTED;