I think I'm getting close to the solution. Thank for your advise and info. But I still can't determine which snapshot comsumes the most space on the volume. When I deleted the snapshot with 28% used 15% total, it transfers the 28% usage and 15% total to the previous snapshot. Do I have to delete ALL snapshots in order to free up the space. The following are the results of df and snap list commands.
bossana>df
/vol/mexico_log2/ 73400320 71608900 1791420 98% /vol/mexico_log2/
/vol/mexico_log2/.snapshot 0 12355224 0 ---% /vol/mexico_log2/.snapshot
-----------------------------------------------------------------------------------------------------------
BOSSANA> snap list mexico_log2
Volume mexico_log2
working...
%/used %/total date name
---------- ---------- ------------ --------
0% ( 0%) 0% ( 0%) Sep 08 12:57 sqlsnap__mexico_09-08-2008_12.56.24
28% (28%) 15% (15%) Aug 19 01:15 sqlsnap__mexico_08-19-2008_01.15.00__daily
29% ( 2%) 16% ( 1%) Aug 18 01:15 sqlsnap__mexico_08-18-2008_01.15.00__daily
29% ( 0%) 16% ( 0%) Aug 17 12:30 sqlsnap__mexico_08-17-2008_12.30.00__weekly
29% ( 0%) 16% ( 0%) Aug 17 01:15 sqlsnap__mexico_08-17-2008_01.15.00__daily
29% ( 0%) 16% ( 0%) Aug 16 01:15 sqlsnap__mexico_08-16-2008_01.15.00__daily
30% ( 0%) 16% ( 0%) Aug 15 01:15 sqlsnap__mexico_08-15-2008_01.15.00__daily
30% ( 1%) 17% ( 0%) Aug 14 01:15 sqlsnap__mexico_08-14-2008_01.15.00__daily