View ASM diskgroup free space

Command

SELECT name,
       state,
       type,
       total_mb/1024                 AS total_gb,
       free_mb/1024                  AS free_gb,
       ROUND((1-free_mb/total_mb)*100,1) AS pct_used,
       usable_file_mb/1024           AS usable_gb
FROM   v$asm_diskgroup
ORDER BY name;

What it does

Shows the total, free and usable (after redundancy) space of each diskgroup.

When to use it

For capacity planning, when space runs low, before deciding to add disks.

Caution

usable_file_mb accounts for redundancy; with NORMAL/HIGH redundancy this column is the real usable space. Query only; no risk.