In a medical dossier you will find all the data about your treatment, such as test results, X-rays, or (referral) letters to a specialist or GP. Your provider is obliged to keep this medical file up to date.
Increasingly, professionals record these data in an electronic patient record. The content of such an electronically stored dossier is the same as that of a paper file. The advantage is that the electronic dossier is easier to access.