I just incidently read that SCNs do get recorded in the archived log files; otherwise how is "Change-Based" recovery possible, which can recover to a SCN before the failure occured. So now we are sure that Oracle has SCNs (what I call commit flags) within the Archive Logs to identify which transactions were committed and which were not.
So now, does it mean that Oracle can definitely identify just the committed transactions from Archive Logs, but applying just that would effect in an increased adverse overhaead as Vijay explained?

Am I getting any clarity here to my original question?

QUESTER