There are three protection modes for the primary database:
Maximum Availability:
Transactions on the primary do not commit until redo information has been written to the
online redo log and the standby redo logs of at least one standby location. If no
standby location is available, it acts in the same manner as maximum performance mode
until a standby becomes available again.
Maximum Performance: Transactions on the primary commit as soon as redo information has
been written to the online redo log. Transfer of redo information to the standby server
is asynchronous, so it does not impact on performance of the primary.
Maximum Protection: Transactions on the primary do not commit until redo information has
been written to the online redo log and the standby redo logs of at least one standby
location. If not suitable standby location is available, the primary database shuts down.