restore not done; all files read only, offline, or already restored

RMAN> restore tablespace  example;

Starting restore at 22-MAY-14
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=23 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=27 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=28 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=29 device type=DISK
allocated channel: ORA_DISK_5
channel ORA_DISK_5: SID=30 device type=DISK

skipping datafile 5; already restored to file +DATA/cvrman/datafile/example.308.847525493
restore not done; all files read only, offline, or already restored
Finished restore at 22-MAY-14

SOLUTION:- restore tablespace example force;

RMAN> restore tablespace example force;

Starting restore at 22-MAY-14
using channel ORA_DISK_1
using channel ORA_DISK_2
using channel ORA_DISK_3
using channel ORA_DISK_4
using channel ORA_DISK_5

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00005 to +DATA/cvrman/datafile/example.308.847525493
channel ORA_DISK_1: reading from backup piece +DATA/cvrman/backupset/2014_05_22/nnndf0_tag20140522t051830_0.290.848207929
channel ORA_DISK_1: piece handle=+DATA/cvrman/backupset/2014_05_22/nnndf0_tag20140522t051830_0.290.848207929 tag=TAG20140522T051830
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:15
Finished restore at 22-MAY-14