Registration of the Schengen transit visa will be required if you leave the transit zone of the airport. Otherwise, it is not necessary to issue a transit visa.

In this case, a transit visa is not needed. You can easily transplant on the existing valid national visa. Another document authorizing entry into Ireland is a UK visa of the category "ordinary or business visitor" provided that you have already had at least one entry to the UK.

A transit visa must be issued in the event that docking takes longer than 24 hours or you plan to leave the airport (sometimes the terminal), waiting for a flight to Dublin. Transit visa, like all other, is issued in advance. The exact list of documents can be found on the Consulate's website.