Affirm/noaffirm, sync/async of log_archive_dest_n According to the documentation, affirm means right after RFS writes redo into SRLs, the standby notifies the primary the redo has been received. Noaffirm means make this acknowlegement even before writing to SRLs (which could fail, hence the name noaffirm). So affirm or noaffirm is about acknowledging receipt of redo on the standby after or before redo write. This is different from sync and async. Sync means the primary is not allowed to commit unless the standby sends back the signal saying it has received the redo. Async means commit can proceed regardless whether the standby has acknowledged that or not. So the two concepts, (no)affirm and (a)sync, are both related to receipt of redo on the standby. However, (no)affirm is an attribute to control the disk I/O behavior of the standby, while (a)sync is to control the primary to standby network behavior.