Total_MB : Size of the disk group in megabytes.
Free_MB : Free space in the disk group in megabytes, without regard to redundancy. From the V$ASM_DISKGROUP view.
[oracle@rac1 ~]$ asmcmd
ASMCMD> lsdg
State Type Rebal Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Name
MOUNTED EXTERN N 512 4096 1048576 546664 206178 0 206178 0 DATA/
[oracle@rac1 ~]$ sqlplus / as sysdba
SQL> SELECT name, free_mb, total_mb, free_mb/total_mb*100 “%” FROM v$asm_diskgroup;
NAME FREE_MB TOTAL_MB %
—————————— ———- ———- ———-
DATA 206178 546664 37.7156718