Recover Standby DB/ Difference beetween NODELAY and UNTIL CHANGE options

Question

Hello,
I have a data guard configuration with two databases (version 10.2.0.3), one primary and one standby.
I have defined a DELAY for apply logs on standby database with following option:
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=DBSTDBY LGWR DELAY=60 SYNC AFFIRM' SCOPE=BOTH;
It works perfectly.
The question is about the fastest way to activate the standby database. To apply all logs received by standby database, I have got two options :
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY;
or
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE UNTIL CHANGE lastchange;
It seems the option NODELAY is faster than the option UNTIL CHANGE.
Why is it faster?

Answer 1

And how do you think you will conserve disk space with RMAN ?
Stop and think about it : How can you revert a database AFTER you have Opened
it Read/Write ? You need to flashback it OR restore it from a backup taken before
the OPEN.
So, you could have taken a backup to Tape or to alternate disk before OPENing the
database. The backup to alternate disk can be via Flashback Recovery area or
a regular RMAN (compressed, you want ?) backup. In the second case, you wouldn't
be using a Flashback mechanism but a simple backup and restore method.