Dublin
The Dublin Regulation determines which member state is responsible to analyze an application for asylum within the EU.
In general, people have to apply for asylum in the country where they first entered Europe. This country, following the hierarchy of principles, will determine which Member State should be responsible for your application.
In Portugal, this decision is made by SEF (Serviço de Estrangeiros e Fronteiras - https://www.sef.pt/), based on information given during the interview on identification, itinerary, grounds for the asylum application, prior stays in Europe and supporting evidence.
The main principle is that only one country within the EU is to be responsible for examining an asylum application.
Tranfers
If you have been transferred to Portugal under Dublin Regulation, you will not face relevant or systematic obstacles in accessing the asylum procedure and reception conditions. You may also reopen your asylum case, after abandoning your application in Portugal.
As a matter of practice, transfers to Greece are suspended.
Appeal
If you are to be transferred to another Member State under the Dublin agreement, you can appeal of the decision.
A person will not be transferred under the Dublin Regulation, if considered that the impact of the transfer would have significant and irremediable consequences for the person, due to a particularly serious mental or physical illness. For that, you will need to be prepared, since medical certificates will be required. It will need to be proven that a transfer would aggravate your health or may cause any act of violence against yourself or others.
According to aida (Asylum Information Database): “applicants within the Dublin procedure were among the most affected by the practice of the Portuguese Bar Association, according to which, following a refusal by the appointed lawyer to provide free legal aid on the grounds that the chances of success were limited, a replacement was not appointed.”