As you are not using Protection Manager, R u using any other Backup Applicatio for this OR you trying to setup this on Netapp directly?
a) First setup "snap sched vol1 0 30 0" => This will create 30 daily snapshots on Netapp1
b) After setting up snapmirror relation to Netapp2:vol2, update the snapmirror.conf to update the snapmirror relation regulary. Try to schedule it so it update the snapmirror after above snapshot is created.
c) Setup a snapvault relation between Netapp2:vol2 and netapp3 - vol3/qtree3 -> configure a snapvault snap sched to a time when snapmirror finishes.
So all 3 runs 1 after another. TR- 3487 will give u more details on Page 19.
Hope it helps