I think I see. You want to retain your volume with all snapshots as of, say today, on your array (primary or secondary). All you need do is change your snapshot policy to none. By doing so, no new snapshots will be created, and none rotated/deleted. You will have to do it manually at the end of your rotation period.
Is that what you were asking? You can check it by setting your policy to none, and checking your next daily. It should still be there.
If you need to lock the volume for legal reasons, you can also do that, but you need to speak to your sales rep to see if you have the license.
Don't forget to quiesce and break your snapmirror if your volume is secondary so it doesn't update the base.