I can assure you that they do not check for positive entry in any database when crossing into Schengen whatsoever. Usually they check if the presented document

I can assure you that they do not check for positive entry in any database when crossing into Schengen whatsoever. Usually they check if the presented document is marked stolen but even that is sometimes skipped as the database (SIS II) is rather slow. This database contains around 50 million entries which shows that it can't possible hold information on all residents. There is neither an EU-wide database of citizens, nor of permanent residents. They do have a database of most issued short-term Schengen visa nowadays (VIS) but even that took a lot of effort to implement. And as said, at the moment they can't even verify all electronic signatures in electronic passports but that should be fixed soon. I'm not even sure how they would create such a database of citizens as even not the German government has a conclusive list of all citizens and I presume it's similar in other member states. That check for the right-of-entry is done with the presented document alone. Revocations are checked against and while it's possible to forge the documents it's not easy. But yes, there are known cases of people successfully entering with forged documents.