I've done some installations for folks who run dual mode (club layout is DC analog).
For a Tsunami, the decoder generally requires 6 volts before the prime mover/air pump start up. From there, you'll get lights and movement when you give more throttle. If your lighting features are set in programming, you won't have things like MARS or ditch lights, beacons and such. You won't have your additional sound features (bell, horn, dynamic brakes, etc.)
One word of caution. The Tsunami has limits on voltages. Don't go over 16 volts DC (you really don't need much over 13 to 14 max). Your DC needs to be clean DC, not pulsed or anything else. The local guys have a club layout with old power packs running on pulse power, which spells eventual death for the decoder.
Symptoms of over voltage and pulse power (aside from hooking up a multimeter to the layout) are erratic running, loss of control, lights flashing 10 times or so. The loco may work for a little, and then just go nuts or stop working.