RMAN error? == What job generates backup piece files in $ORACLE_HOME?

Question

Dear experts,
I noticed that I have hundreds of files in $ORACLE_HOME that are backup pieces. I have set up the backup location in +FRA.  I am not sure how these files get generated and why the cause an error when RMAN ran as you can see below.
I very much appreciate your assistance,
Terry
RMAN> DELETE NOPROMPT OBSOLETE;
RMAN retention policy is set to recovery window of 3 days
Deleting the following obsolete backups and copies:
Type Key Completion Time Filename/Handle
Backup Set 319 21-JUN-08
Backup Piece 271 21-JUN-08 +FRA/bms/autobackup/2008_06_21/s_657944280.306.657944281
Backup Set 322 21-JUN-08
Backup Piece 274 21-JUN-08 bk_324_1_657950801
Backup Set 323 21-JUN-08
Backup Piece 275 21-JUN-08 c-118945620-20080621-02
Backup Set 333 22-JUN-08
Backup Piece 283 22-JUN-08 /u01/app/oracle/product/10.2.0/db_1/afjjhg2v_1_1
Backup Set 348 23-JUN-08
Backup Piece 296 23-JUN-08 /u01/app/oracle/product/10.2.0/db_1/aujjk4el_1_1
Backup Set 363 24-JUN-08
Backup Piece 309 24-JUN-08 /u01/app/oracle/product/10.2.0/db_1/bdjjmonm_1_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of delete command at 06/25/2008 02:00:23
RMAN-06091: no channel allocated for maintenance (of an appropriate type)

Answer 1

The confusion is that I have a server that deletes the files based on the retention period and has no issues. The other server has identical setup, but it gives an error and it does not delete the backup piece.
Backup Piece 1402 25-JUN-08 /u01/app/oracle/product/10.2.0/db_1/jbjjpc9a_1_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of delete command at 06/26/2008 02:00:21
RMAN-06091: no channel allocated for maintenance (of an appropriate type)
$ORACLE_HOME files generated from the channel fornat:
-rw-r----- 1 oracle oinstall 294626304 Jun 25 07:06 rcjjpu2r_1_1
-rw-r----- 1 oracle oinstall 98304 Jun 25 07:07 rdjjpu4m_1_1
-rw-r----- 1 oracle oinstall 244966912 Jun 26 07:07 rljjsifj_1_1
-rw-r----- 1 oracle oinstall 98304 Jun 26 07:07 rmjjsih3_1_1
Files generated from +FRA pfile location:
ASMCMD> pwd
+FRA/DBWS/BACKUPSET
ASMCMD> ls -ltr
Type Redund Striped Time Sys Name
Y 2008_06_15/
Y 2008_06_16/
Y 2008_06_17/
Y 2008_06_18/
Y 2008_06_19/
Y 2008_06_20/
Y 2008_06_21/
Y 2008_06_22/
Y 2008_06_23/
Y 2008_06_24/
Y 2008_06_25/
Y 2008_06_26/
ASMCMD> cd 2008_06_26/
ASMCMD> ls -ltr
Type Redund Striped Time Sys Name
BACKUPSET MIRROR COARSE JUN 26 07:00:00 Y ncnnf0_TAG20080626T070124_0.1101.658393401
BACKUPSET MIRROR COARSE JUN 26 07:00:00 Y nnndf0_TAG20080626T070124_0.1159.658393287
BACKUPSET MIRROR COARSE JUN 26 07:00:00 Y nnndf0_TAG20080626T070124_0.850.658393285