The majority of universities will require you to obtain at least 40% in an exam for you to pass it. If the pass grade isn’t achieved you generally have to re-take the exam in the ‘Retake Period’ before you can progress to the next year of your degree course
If you do have to do any re-takes try and get feedback on what was wrong in your exam answer which meant you didn’t pass. You can then take this on to the re-sit exam and hopefully will pass the re-take.
Summer re-takes are often in the summer holidays so the last thing you’ll want to do is give up a holiday for exams!