snap list [volume name] 
output:  (for instance) 
  %/used  %/total  date          name
  ----------  ----------  ------------  --------
  25% ( 1%)    8% (0%)  Feb 28 02:37  Daily.23  
  31% (11%)   12% ( 3%)  Feb 12 02:37 Daily.28 (busy,LUNs)
  36% (10%)   14% (3%)  Feb 04 02:13  monthly.FB032008 
lun snap usage -s [vol name] [busy snapshot name]
Snapshot - Daily.7
Snapshot - MR162008
Snapshot - Daily.8  
Snapshot - Daily.9
this is an example of how it could be, however you have to delete all listed snapshots
snap delete -V [volume name] [snapshot name]
PS:  you might set vol options snap reserve [vol name] a bit less, for instance 10% instead of default 20 (if it set) it gives you a bit of "breathing" space on volume 
worked for me hope it helps 
Message was edited by: Victor Safonov