Abstract: A "mobile" Deployment Manager is one that is capable of being started on different MVS images in the Sysplex. This provides higher availability because it allows you to maintain a DMGR instance even when MVS images are taken out of service for planned maintenance. It's a relatively simple thing to accomplish, and is considered a "best practice" when configuring a network deployment configuration that spans multiple MVS images in a Sysplex.
At the heart of this is z/OS Sysplex Distributor. That's what allows the DMGR to be started in different places and still be located by a TCP request.
This document covers two scenarios: planning for a mobile DMGR from the very beginning, before you've started to build the cell; and updating an existing configuration and make the DMGR have the ability to be mobile.