To upgrade to NSX 6.3.x in a cross-vCenter environment, you must upgrade the NSX components in the order in which they are documented in this guide.
NSX components must be upgraded in the following order:
Primary NSX Manager appliance
All secondary NSX Manager appliances
NSX Controller cluster
The upgrade process is managed by the NSX Manager. If the upgrade of a component fails or is interrupted and you need to repeat or restart the upgrade, the process begins from the point at which it stopped; it does not start over from the beginning.
The upgrade status is updated for each node and at the cluster level.