Only one of your options is syntactically correct:c:\users\john>rman target /
Recovery Manager: Release 12.1.0.1.0 - Production on Tue Dec 24 13:45:03 2013
Copyright (c) 1982, 2013, Oracle and/or its affiliates. All rights reserved.
connected to target database: ORCLZ (DBID=2051912303)
RMAN> backup current controlfile;
Starting backup at 2013-12-24 13:45:12
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=258 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
channel ORA_DISK_1: starting piece 1 at 2013-12-24 13:45:15
channel ORA_DISK_1: finished piece 1 at 2013-12-24 13:45:16
piece handle=C:\APP\ORACLE\FAST_RECOVERY_AREA\ORCLZ\BACKUPSET\2013_12_24\O1_MF_NCNNF_TA
224T134514 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 2013-12-24 13:45:16
RMAN> backup controlfile copy;
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00558: error encountered while parsing input commands
RMAN-01009: syntax error: found "controlfile": expecting one of: "archivelog, as, auxil
el, check, controlfilecopy, copies, copy, cumulative, current, database, database root,
name_convert, db_recovery_file_dest, device, diskratio, duration, filesperset, force, f
maxsetsize, nochecksum, noexclude, nokeep, not, pluggable, pool, proxy, recovery, reuse
lespace, tag, to, validate, ("
RMAN-01007: at line 1 column 8 file: standard input
RMAN>