Hi Michal, the ftpdocs you referenced is an old version of the documentation for CA Datacom/DB Version 15.0, and the techdocs webpage is for CA Datacom/AD Version 15.1 - two different products.
So the first question is - which product are you trying to upgrade - CA Datacom/AD or CA Datacom/DB?
The next question is - if CA Datacom/AD, what products at your firm use CA Datacom/AD for their data repository? This information will help us put you on the right track.
The short answer to either product is that you should follow the process for an Active Upgrade, as it uses existing files and configurations, and has proven to be a simpler upgrade. There are other considerations, though, which is why I asked the above two questions.
I hope to hear from you soon!