As per Oracle Note:312737.1

The Oracle DiskSbt API is designed for TESTING purposes ONLY
and can NOT be used for any database backup.

The Oracle.Disksbt can be used to simulate tape backups on disk using sbt_tape
channel.


[oracle@canada ~]$ rman target = / nocatalog

Recovery Manager: Release 11.2.0.1.0 - Production on Thu Dec 27 18:53:45 2012

Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved.

connected to target database: DELL (DBID=3764293269)
using target database control file instead of recovery catalog

RMAN> run {
2> allocate channel 't1' type 'sbt_tape'
3> parms 'SBT_LIBRARY=oracle.disksbt, ENV=(BACKUP_DIR=/u01/backup)';
4> backup database plus archivelog format='%U';
5> }


Code:
allocated channel: t1
channel t1: SID=46 device type=SBT_TAPE
channel t1: WARNING: Oracle Test Disk API


Starting backup at 27-DEC-12
current log archived
channel t1: starting archived log backup set
channel t1: specifying archived log(s) in backup set
input archived log thread=1 sequence=3 RECID=1 STAMP=803155707
input archived log thread=1 sequence=4 RECID=2 STAMP=803155714
input archived log thread=1 sequence=5 RECID=3 STAMP=803155911
input archived log thread=1 sequence=6 RECID=4 STAMP=803156172
channel t1: starting piece 1 at 27-DEC-12
channel t1: finished piece 1 at 27-DEC-12
piece handle=02ntuc6c_1_1 tag=TAG20121227T185612 comment=API Version 2.0,MMS Version 8.1.3.0
channel t1: backup set complete, elapsed time: 00:00:01
Finished backup at 27-DEC-12

Starting backup at 27-DEC-12
channel t1: starting full datafile backup set
channel t1: specifying datafile(s) in backup set
input datafile file number=00001 name=/u01/app/oracle/oradata/dell/system01.dbf
input datafile file number=00002 name=/u01/app/oracle/oradata/dell/sysaux01.dbf
input datafile file number=00005 name=/u01/app/oracle/oradata/dell/example01.dbf
input datafile file number=00003 name=/u01/app/oracle/oradata/dell/undotbs01.dbf
input datafile file number=00004 name=/u01/app/oracle/oradata/dell/users01.dbf
channel t1: starting piece 1 at 27-DEC-12
channel t1: finished piece 1 at 27-DEC-12
piece handle=03ntuc6e_1_1 tag=TAG20121227T185613 comment=API Version 2.0,MMS Version 8.1.3.0
channel t1: backup set complete, elapsed time: 00:02:03
channel t1: starting full datafile backup set
channel t1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel t1: starting piece 1 at 27-DEC-12
channel t1: finished piece 1 at 27-DEC-12
piece handle=04ntuca9_1_1 tag=TAG20121227T185613 comment=API Version 2.0,MMS Version 8.1.3.0
channel t1: backup set complete, elapsed time: 00:00:01
Finished backup at 27-DEC-12

Starting backup at 27-DEC-12
current log archived
channel t1: starting archived log backup set
channel t1: specifying archived log(s) in backup set
input archived log thread=1 sequence=7 RECID=5 STAMP=803156303
channel t1: starting piece 1 at 27-DEC-12
channel t1: finished piece 1 at 27-DEC-12
piece handle=05ntucah_1_1 tag=TAG20121227T185824 comment=API Version 2.0,MMS Version 8.1.3.0
channel t1: backup set complete, elapsed time: 00:00:01
Finished backup at 27-DEC-12
released channel: t1