Move items to new VertIGIS Server

Hello,

We have a VertiGIS server connected to our ArcGIS Portal. A new VertiGIS server is ready to replace the current one, which will also change the URL. This server is already connected to our Portal.

What's the best approach? 
The items in ArcGIS Portal already work in both environments. When I access items in the new environment, I can also open items where the old URL is still in the JSON. How does this work exactly? Can I simply change the URL and the JSON without the item no longer working? Or is there more to it (which is likely)?

Thanks in advance.