Creating ASM diskgroup using "asmcmd"

Created a "TEMP" diskgroup consisting single LUN with external redundancy.

ASMCMD [+] >  mkdg '<dg name="temp" redundancy="external"><dsk string="ORCL:ASM_0004"/></dg>'

If this is a RAC, then this diskgroup needs to be mounted on all other nodes manually. You can do so by starting asmcmd on other nodes:

ASMCMD [+] > mount TEMP
ASMCMD [+] > lsdg
State    Type    Rebal  Sector  Block       AU  Total_MB  Free_MB  Req_mir_free_MB  Usable_file_MB  Offline_disks  Voting_files  Name
MOUNTED  EXTERN  N         512   4096  1048576     20473    20380                0           20380              0             N  TEMP/
MOUNTED  NORMAL  N         512   4096  1048576     61419    60493            20473           20010              0             Y  VOTE_DG/