Message Oracle RMAN-05018 - some datafile copies cannot be recovered, aborting the RECOVER command

ERRORsome datafile copies cannot be recovered, aborting the RECOVER command
CAUSEThis error message can follow one or more RMAN-5017 or RMAN-5019 error messages.
ACTIONSee RMAN-5017 or RMAN-5019 error messages documentation for more information.