Oracle Message ORA-15471 - volume redundancy incompatible with diskgroup redundancy

ERRORvolume redundancy incompatible with diskgroup redundancy
CAUSEAn ADD VOLUME command specified a volume redundancy that was incompatible with the diskgroups redundancy.
ACTIONSpecify a valid volume redundancy. A volume cannot have external redundancy with a high redundancy diskgroup. Also, a volume cannot have high redundancy with an external redundancy diskgroup.