DataGuard: diff between sync async

[Rayyah]

Synchronous : The synchronous redo transport mode transmits redo data synchronously with
respect to transaction commitment. A transaction cannot commit until all redo generated by that transaction has been successfully sent to every enabled redo transport destination that uses the synchronous redo transport mode.This transport mode is used by the Maximum Protection and Maximum Availability data protection modes .
Asynchronous : The asynchronous redo transport mode transmits redo data asynchronously with respect to transaction commitment. A transaction can commit without waiting for the redo generated by that transaction to be successfully sent to any redo transport destination that uses the asynchronous redo transport mode.This transport mode is used by the Maximum Performance data protection mode .