Upgrade of custom application

Dear community,

we are a company located in central Germany working with Intersystems Caché since 2003 (Jesus, that's actually a long time in IT).

As we struggle to keep pace with outside development we still operate on Caché 2013.1

We are, of course, aware that we need to upgrade Caché and therefor plan an upgrade to 2017.2.

Now my question to you bold ObjectScript warriors: