Moving Portal to new sub-domain

JeffPace1

We would like to migrate our enterprise portal from www.domain.org to gis.domain.org

I understand the work involved, but has a solution ever been devised for hosted layers? WE have 10ks of items.  

Stack:
HA Portal
HA Web Adapters
10 HA AGS sites (including Hosting with relational, tile, and BSS datastores)

Trying to come up with any sort of plan.

ReeseFacendini

You'll need to work with Esri Professional Services to complete that DNS migration. Otherwise changing the DNS of Enterprise is not supported and will break the system.