Oracle Exam 1Z0-066 Topic 6 Question 21 Discussion

The Maximum Availability protection mode provides the highest level of data protection that is possible without compromising the availability of a primary database. Transactions do not commit until all redo data needed to recover those transactions has been written to the online redo log and to at least one synchronized standby database. If the primary database cannot write its redo stream to at least one synchronized standby database, it operates as if it were in maximum performance mode to preserve primary database availability until it is again able to write its redo stream to a synchronized standby database.

This mode ensures that no data loss will occur if the primary database fails, but only if a second fault does not prevent a complete set of redo data from being sent from the primary database to at least one standby database.

When a transport is performed using SYNC/AFFIRM, the primary performs write operations and waits for acknowledgment that the redo has been transmitted synchronously to the physical standby and written to disk. A SYNC/AFFIRM transport provides an additional protection benefit at the expense of a performance impact caused by the time required to complete the I/O to the standby redo log.