RMAN backup validate database on databases in noarchivelog mode

Starting with 11g RMAN seems to allow a “backup validate database” even if the database is not in archive log mode:

SQL*Plus: Release 11.2.0.2.0 Production on Wed Mar 23 11:18:01 2011
Copyright (c) 1982, 2010, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            /u01/oradata/ORA11/archive
Oldest online log sequence     140
Current log sequence           143

As you can see from the listing above the database is not in archive log mode. Nevertheless doing a “backup validate database” works:

<hostname>:/tmp# rman target /
Recovery Manager: Release 11.2.0.2.0 - Production on Wed Mar 23 11:18:25 2011
Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.
connected to target database: ORA11(DBID=12345678)
RMAN> backup validate datafile 1;
Starting backup at 23-MAR-11
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=124 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=/u01/oradata/ORA11/system01.dbf
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:07
List of Datafiles
=================
File Status Marked Corrupt Empty Blocks Blocks Examined High SCN
---- ------ -------------- ------------ --------------- ----------
1    OK     0              47774        307200          404393656
File Name: <name>
Block Type Blocks Failing Blocks Processed
---------- -------------- ----------------
Data       0              237701
Index      0              19286
Other      0              2439

Doing the same with a 10g database yields:

<hostname>:/tmp# rman target /
Recovery Manager: Release 10.2.0.5.0 - Production on Wed Mar 23 11:19:20 2011
Copyright (c) 1982, 2007, Oracle.  All rights reserved.
connected to target database: ORA10 (DBID=12343456)
RMAN> backup validate datafile 1;
Starting backup at 23-MAR-11
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=201 devtype=DISK
channel ORA_DISK_1: starting full datafile backupset
channel ORA_DISK_1: specifying datafile(s) in backupset
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 03/23/2011 11:19:27
ORA-19602: cannot backup or copy active file in NOARCHIVELOG mode