Q: see above.

I have a view that uses a synonym (table on another instance accessed through a database link). When I perform a database search and include views, the buttons for commit/rollback are enabled.

Why? Is this reported by Oracle and if so, why?

It is because every select statement over a dblink starts a transaction, and you should commit after every select over dblink.

OK, but Marco, is it possible, that PLD auto-commits after a search to make sure that the buttons are disabled again?

PL/SQL Developer will only commit when all records are fetched. If it would commit before that, fetching subsequent records would lead to "ORA-01002: fetch out of sequence".

OK, but PLD does not commit, even after the search is finished. For the user, it looks odd.