How to check used or free disk space in ASM Instance

With asmcmd lsdg command it will be displayed mounted disk groups lists and their information. In fact, lsdg queries V$ASM_DISKGROUP_STAT by default and shows disk groups information.

The syntax of lsdg command is as follows,
lsdg [-gH][--discovery][pattern]

If the --discovery flag is specified, then it is queried the V$ASM_DISKGROUP view. The output also includes notification of any current rebalance operation for a disk group. If a disk group is specified, then lsdg returns only information about that disk group.

If -g option is specified then it selects from GV$ASM_DISKGROUP_STAT, or from GV$ASM_DISKGROUP if the --discovery flag is also specified.

From the lsdg command,

Total_MB indicates the size of the disk group in megabytes.

Free_MB indicates free space in the disk group in megabytes, without regard to redundancy. From the V$ASM_DISKGROUP view.

Req_mir_free_MB indiates the amount of space that must be available in the disk group to restore full redundancy after the most severe failure that can be tolerated by the disk group. This is the REQUIRED_MIRROR_FREE_MB column from the V$ASM_DISKGROUP view.

Usable_file_MB indicates the amount of free space, adjusted for mirroring, that is available for new files.

You can directly query from v$asm_diskgroup or V$ASM_DISKGROUP_STAT view or you can issue lsdg within asmcmd tool.

From the V$ASM_DISKGROUP view,

SYS@EAI1>SELECT name, free_mb, total_mb, free_mb/total_mb*100 "%" FROM v$asm_diskgroup;

NAME FREE_MB TOTAL_MB %
------------------------------ ---------- ---------- ----------
DISKGROUP1 112168 245754 45.6423904

From ASMCMD,

ASMCMD> lsdg
State Type Rebal Unbal Sector Block AU Total_MB Free_MB Req_mir_free_MB Usable_file_MB Offline_disks Name
MOUNTED EXTERN N N 512 4096 1048576 245754 112168 0 112168 0 DISKGROUP1/