This is a followup to https://vmscribble.com/vcenter/vcenter-6-upgrade-options-to-enable-cross-vcenter-vmotion-in-the-same-sso-domain/ Where you already have a brand new 6.0 VCSA (external PSC) and want the 5.5 windows VC upgrade to be on the same SSO domain. Option A
Install a new 6.0 VC (new SSO domain). Upgrade the current windows 5.5 VC to 6.0. Un-install the window 6.0 VC. Re-install 6.0 choosing the 6.0 VCSA SSO domain (external PSC). This will allow you to drain the upgraded 5.5 VC so it can be decommissioned (using esxi 6.0 and cross vcenter vmotion)
Note – Even though the new 6.0 and existing/upgraded 5.5 VC’s have vpshere.local as the SSO domain name, they are NOT on the same SSO domain. It is tricky.
You will lose tags, custom VC roles and user permissions for all objects (even at the root VC level.. You will have to re-join to AD.