Basic ASM Commands

Most commonly used ASM Commands

chdg :  Changes a disk group (add, drop, rebalance, or migrate on the Exadata appliance).

chkdg : Checks or repairs a disk group.

iostat : Displays I/O statistics for disks.

lsattr :  Lists the attributes of a disk group.

lsdg : Lists disk groups and their information.

lsdsk : Lists disks Oracle ASM disks.

lsod : Lists open devices.

mkdg : Creates a disk group.

mount : Mounts a disk group.

umount : Dismounts a disk group.

offline : Offlines a disk or a failure group.

online : Onlines a disk or a failure group.

rebal : Rebalances a disk group.

dropdg : Drops a disk group.

Query to check ASM Disk groups usage and free space:

set pages 300

set lines 400

select name,allocation_unit_size,Total_mb,free_mb, (free_mb/total_mb)*100 "free %", usable_file_mb, (usable_file_mb/total_mb)*100 "usable free %"  from  V$ASM_DISKGROUP_STAT;

Reference:

https://docs.oracle.com/en/database/oracle/oracle-database/21/ostmg/asmcmd-diskgroup-commands.html#GUID-3BA40908-0543-4968-B834-BD4D873E1059