Oracle Message RMAN-06478 - WARNING: datafile copy string cannot be found on disk

ERRORWARNING: datafile copy string cannot be found on disk
CAUSEThe CHANGE DATAFILECOPY AVAILABLE command was used, but the datafile copy cannot be found on disk.
ACTIONIf the storage containing the datafile copy has been removed from the host, restore it and retry the command. If the datafile copy is permanently gone, then issue the CHANGE DATAFILECOPY DELETE command for this datafile.