You might want to create an extra backup Snapshot copy on the source and destination in a qtree SnapMirror relationship. You can create a manual Snapshot copy using the snap create command. Then, you can use the -c and -s options of the snapmirror update command together to establish an extra backup Snapshot copy on both sides of a SnapMirror qtree relationship.
snapshot_name is the name of the Snapshot copy.
systemB> snap create vol2 my_snapThis creates a Snapshot copy, my_snap, of the volume vol2.
src_snap is the name of the Snapshot copy on the source.
dest_snap is the name of the Snapshot copy on the destination.
destination is the name of the destination.
systemA> snapmirror update -S systemB:/vol/vol2/qtree1 -s my_snap -c my_dest_snap vol/vol4/qtreeSafe