At KIT the oral exam is either done as a colloquium or as a doctoral viva. Please refer to the respective doctoral ordinance to see which exam type applies for your KIT department. Normally you will be told the overall result of your doctorate right after your oral exam.
The colloquium includes a scientific presentation, generally about your dissertation, as well as a subsequent discussion, known as the disputation.
The doctoral viva originated in a time in which doctoral researchers concluded their studies along with their doctoral research project. It is similar to a final exam, which is usually done in one main subject and two subsidiary subjects.