Thanks Pradeep for time to read and respond to my query.
This is event not a alarm. Here is a complete details from notification e- mail.
An Error event at 10 Jun 06:08 SGT on Active/Active
Controller XYZ.dc.ABC.com:
Global Status: NonCritical; There are not enough spare disks. /aggr0_SAS/plex0/rg0: Please add spare disks to any pool supporting block checksums with minimum size: Used 418000/856064000 (MB/blks).
Also can you detail more as how alarm (DFM) is different than event. As much as DFM is concerned, mostly it is events like error, warning etc....
Thanks,
VM