Cause: An attempt was made to use a feature which is not permitted by the diskgroup's redundancy policy. Common examples are forcibly dropping a disk from an EXTERNAL REDUNDANCY diskgroup, using the FAILGROUP clauses with an EXTERNAL REDUNDANCY diskgroup, or using invalid template attributes. See the solution below.
Error solution: Omit the option from the command.
Database version: Oracle 11g Release 2 (11.2)