To use SnapMirror to copy a qtree, you do not create a destination qtree because the snapmirror initialize command creates it. The volume where you want the destination qtree to be must be online. After the destination qtree is initialized, it is no longer writable. However, the rest of the volume where that qtree resides is still writable.
The destination Snapshot copy created by qtree initialization is marked busy in the output of the snap list command until the next transfer is complete.