I was trying to take backup of database in Oracle 11g by using RMAN
$ rman target /
Recovery Manager: Release 11.2.0.1.0 - Production on Fri Sep 11 10:14:37 2015
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connected to target database: ORCL (DBID=1415405400)
RMAN> backup incremental level 0 as compressed backupset database;
Starting backup at 11-SEP-15
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=1 device type=DISK
RMAN-06169: could not read file header for datafile 5 error reason 4
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup command at 09/11/2015 10:16:58
RMAN-06056: could not access datafile 5
I have misplaced the datafile then I have added that datafile executing a touch command but still I was getting an error that the database is unable to lock the file. I put the database in mount mode then I took that file offline and after I started backup there was the same error. So how can I solve this error without getting tablespace deleted