Word of warning: When you get to vSphere 6.5, your vCenter Servers are stuck to whatever PSC Site they are currently located in!
In vSphere 5.1 and 5.5 you had the freedom to re-point the Inventory Service, vSphere Web Client, and vCenter Server services to any SSO you liked. Different Site, different domain, there were no restrictions (other than the process was admittedly cumbersome)
With vSphere 6.0 GA this functionality regressed severely to the point that you could only repoint vCenters between PSCs in the same Site. No more repointing to a different site and no more repointing to a completely new SSO Domain. Thankfully with vSphere 6.0 U1 the ability to repoint between sites was introduced but move between SSO Domains remained impossible (outside of a re-install of the vCenter).
In vSphere 6.5 the ability to repoint vCenters between sites is no longer available. When you deploy or upgrade to vSphere 6.5, your vCenter Servers are stuck to whatever PSC Site it currently resides.
If you need to move a vCenter Server to a different PSC Site or a different SSO Domain, you need to re-install that vCenter Server.
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