You’ll have a lot of information that can help you in the viva. Ideas, questions, answers, reading, references, facts and figures. You’ll need to know a lot of things to get you to the viva, and of course, to get you through the viva.
As essential as these things are, remember that your examiners will be more interested in the insights that you have: how you think about a topic rather than simply what you know about a topic. What conclusions you reached, rather than simply the results you got.
The viva is not simply a test of what you remember. What do you know?