The manual is not very clear so what is the difference between the following Data Guard Redo Transport parameters
LGWR SYNC AFFIRM
and
LGWR SYNC NOAFFIRM

Our parameter is set to LGWR SYNC NOAFFRIM but how can the asynchronous NOAFFIRM be used with SYNC?

The manual states that with the SYNC option the log writer process waits for the I/O to complete before continuing.

It also states that for NOAFFIRM the log writer process does NOT wait until the disk I/O completes before continuing.

(1) So what is happening when SYNC and NOAFFIRM are used together?
(2) What is the difference between SYNC and AFFIRM parameters. The manual seems to suggest they do the same thing. If so what are they both available?