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.