• Calculating ASM diskgroup Usable Size | OracleNext - Solution to your Oracle problems.
  select name, TOTAL_MB, FREE_MB, REQUIRED_MIRROR_FREE_MB, USABLE_FILE_MB from v$asm_diskgroup where group_number=2;
  in Oracle > DB 11g with 11g asm diskgroup lsdg required_mirror_free_mb size total_mb usable vasm_diskgroup

total_mb from all users