How to add a disk to an ASM disk group in Oracle

Add one or more disks to an ASM disk group. ASM rebalances automatically to spread data onto the new storage. Run connected to the ASM instance AS SYSASM.

Adding disks starts a rebalance that moves data and can run for a while under I/O load. Confirm the new disk path is correct and discoverable, and pick a REBALANCE POWER suited to the window.

ALTER DISKGROUP &&dg_name
  ADD DISK '&disk_path'
  REBALANCE POWER 4;

-- Verify (read-only): the new disk
SELECT name, path, total_mb, free_mb, mount_status, header_status
FROM   v$asm_disk
WHERE  group_number = (SELECT group_number FROM v$asm_diskgroup
                       WHERE name = UPPER('&dg_name'));

-- Rebalance progress
SELECT operation, state, power, est_minutes
FROM   v$asm_operation;