2 VCSA instances have been deployed, each as a separate instance with embedded PSC but have not been linked.
Now that they are up and running, how can they be put into linked mode?
Check if the following VMware KB article helps: world-line
vCenter Embedded Linked Mode for a vCenter Server Appliance with Embedded Platform Services Controller
vCenter Server 6.7 U2 architecture improvements – 4sysops
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