This is a case for a controlfile copy that does not want to be deleted, no matter what.
Trying to delete file control file copy seems to succeed:
RMAN> delete controlfilecopy '/mnt/backup/db/rman/20151127_173502/snapcf_catdb.f';
released channel: ORA_DISK_1
released channel: ORA_DISK_2
released channel: ORA_DISK_3
released channel: ORA_DISK_4
released channel: ORA_DISK_5
released channel: ORA_DISK_6
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=270 instance=db device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=499 instance=db device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=533 instance=db device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=566 instance=db device type=DISK
allocated channel: ORA_DISK_5
channel ORA_DISK_5: SID=602 instance=db device type=DISK
allocated channel: ORA_DISK_6
channel ORA_DISK_6: SID=696 instance=db device type=DISK
List of Control File Copies
===========================
Key S Completion Time Ckp SCN Ckp Time
------- - --------------- ---------- ---------------
1 X 27-NOV-15 22062510 27-NOV-15
Name: /mnt/backup/db/rman/20151127_173502/snapcf_db.f
Tag: TAG20151127T173858
Do you really want to delete the above objects (enter YES or NO)? YES
deleted control file copy
control file copy file name=/mnt/backup/db/rman/20151127_173502/snapcf_db.f RECID=1 STAMP=896915639
Deleted 1 objects
But the file is still there, as shown from the crosscheck copy command, or from the report obsolete
RMAN> crosscheck copy;
released channel: ORA_DISK_1
released channel: ORA_DISK_2
released channel: ORA_DISK_3
released channel: ORA_DISK_4
released channel: ORA_DISK_5
released channel: ORA_DISK_6
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=270 instance=db device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=499 instance=db device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=533 instance=db device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=566 instance=db device type=DISK
allocated channel: ORA_DISK_5
channel ORA_DISK_5: SID=602 instance=db device type=DISK
allocated channel: ORA_DISK_6
channel ORA_DISK_6: SID=696 instance=db device type=DISK
specification does not match any datafile copy in the repository
validation failed for control file copy
control file copy file name=/mnt/backup/db/rman/20151127_173502/snapcf_db.f RECID=1 STAMP=896915639
Crosschecked 1 objects
The solution is to uncatalog the file, as folow:
RMAN> change controlfilecopy '/mnt/backup/db/rman/20151127_173502/snapcf_db.f' uncatalog;
uncataloged control file copy
control file copy file name=/mnt/backup/db/rman/20151127_173502/snapcf_db.f RECID=1 STAMP=896915639
Uncataloged 1 objects
Now the controlfile copy is not anymore listed from any command:
RMAN> crosscheck copy;
released channel: ORA_DISK_1
released channel: ORA_DISK_2
released channel: ORA_DISK_3
released channel: ORA_DISK_4
released channel: ORA_DISK_5
released channel: ORA_DISK_6
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=270 instance=db device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=499 instance=db device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=533 instance=db device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=566 instance=db device type=DISK
allocated channel: ORA_DISK_5
channel ORA_DISK_5: SID=602 instance=db device type=DISK
allocated channel: ORA_DISK_6
channel ORA_DISK_6: SID=696 instance=db device type=DISK
specification does not match any datafile copy in the repository
specification does not match any control file copy in the repository
validation succeeded for archived log