I'm not sure if they will not allow you to sit for the exam, but if you fail your TMA and quiz (i.e. less than 40% for OCAS as onelastwish said) then please don't sit for it. No matter how well you do your grade will be counted as a fail and you would have to repeat the module. Although a few of my lecturers did say that if your OCAS score is borderline (e.g. 39%) then they'll try and push you to a pass.. I guess it's up to you but personally I wouldn't take the chance :/
