Database Software

I have following backup script:

allocate channel ch1 type $CHANNEL_TYPE;
backup as compressed backupset
incremental level 0
format '${RMBKUPDIR}dbfile_%U%_%t'
database;

# switch current archived log, so there is at least
# one archived log to backup in next command.
sql 'ALTER SYSTEM ARCHIVE LOG CURRENT';

# now backup archived logs
backup as compressed backupset
archivelog like '$ARCHDIR/%.arc' format '${RMBKUPDIR}arlog_%U%_%t'
delete input;

Which was completed let us say at 5:15 PM


I see my rman log that a control file backup was also done towards the end:
Finished backup at 2013-03-31 17:15:22

Starting Control File and SPFILE Autobackup at 2013-03-31 17:15:22
piece handle=c-38338326-20130331-07 comment=API Version 2.0,MMS Version 5.0.0.0
Finished Control File and SPFILE Autobackup at 2013-03-31 17:18:01
released channel: ch1


Now I am doing point in time restore:

1. I first retsore control file from c-38338326-20130331-07

2. I then specify set until time to 6:00PM (45 minutes after backup..)
and then do restore.

When rman restore completes, it errors that system and some other database files reuqires more recovery?
I cannot open database with restelogs option. Why?

I thought my backup is self contained in the sense that I did archive log backup towards the end of my script; so only those archived logs should be needed. But it is requesting additional archive logs; only when they are retsored and applied; I can open my database with resetlogs.

Should I have specied set until time to 5:18PM instead of 6:00PM. Would that have made a difference?