How to Drop ASM Datagroup while not mounted and disks corrupted

In a test environment we accidentally corrupt asm disks and reset their headers. When I query V$ASM_DISK view, I saw that disks were discovered as "CANDIDATE". It was like newly added disks available for ASM. The problem was, my datagroup which was using these disks, was exists but i could not drop it. That was because a diskgroup has to be mounted in order to be dropped, but its disks were corrupted so i could not mount it:

SQL> drop diskgroup DATA;
drop diskgroup DATA
*
ERROR at line 1:
ORA-15039: diskgroup not dropped
ORA-15001: diskgroup "DATA" does not exist or is not mounted


SQL> ALTER DISKGROUP DATA mount;
ALTER DISKGROUP DATA mount
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15017: diskgroup "DATA" cannot be mounted
ORA-15063: ASM discovered an insufficient number of disks for diskgroup "DATA"

How can i drop/delete datagroup which i can not mount?

Solution is to create a new datagroup, add all disks to new datagroup. At the end, old datagroup disappears... Then you may drop newly added diskgroup.

create diskgroup DATA_DROP external redundancy disk '/dev/rhdisk#' force;
alter diskgroup DATA_DROP add disk '/dev/rhdisk#';
...
DATA disappears when i add all its disks to DATA_DROP...
...
drop diskgroup DATA_DROP including contents;

now, DATA diskgroup has gone and all its disks are in "FORMER" status.