I am taking my history PhD oral comps in two weeks. Comps in my department are like fight club - no one talks about it. I have no idea what to expect for two of my fields. I did get some indication of vague questions for my Middle East and American fields, but nothing for Modern Germany and 19th century Europe. My written covered fall of Weimar, Bismarkian Diplomacy, Congress of Vienna, Holocaust Historiography, Revs of 1848, inevitability of WWI, Sonderweg, and rise of Hitler. Germany prof is devoted to historiography, 19th century to narrative. Between the two fields, my book list is a little over 400. I'm simply overwhelmed and would so very much appreciate any advice on what to expect! With a three hour exam, I am guessing about 40 per field, or perhaps it is combined. I get the sense that it ends with my signature in blood to never discuss what went on behind those closed doors.
UIUC's History Department has digitized a number of their past preliminary questions. Although they may be a bit out of date, they do offer a window into the thought processes behind the exam process. The UIUC history grad school page also has a more exam questions and advice on approaching it. While UIUC's questions will likely not match the your program's exact specifics, it can help.
The other advice I would give you as someone who went through this process is to try and suss out exactly what your professor wants out of these exams. Some professors take an approach in which they want you to demonstrate that you can teach this material, others want to see a firm command of the factual and theoretical facets of historical scholarship. Another good thing to do, especially in the oral defense, is to try and give some idea how reading all of these books will somehow inform your future dissertation. In the case of your Germanist/Europeanist, I would suggest trying to take this massive list and group them historiographically with close attention to how they interact and connect into the larger whole.
If you have a specific time limit for your defence, use that to your advantage. If you get asked a question that you are well prepared to answer, keep talking.
Comps are like a hazing. You will get asked questions that will make you feel stupid and as if you don't belong there. Some profs revel in doing just that, while others really want you to succeed. One of my profs told me before that my essays were great and I was going to do wonderfully, then ripped me to shreds. I ended up talking the most about Colonial Latin America, not even my primary area, but the prof clearly wanted to help me along. Read the temperature of the room and remember, no matter what, it'll be over in two hours (or whatever).
Honestly, I would write my dissertation again. I would never do comps a second time.
For me, it varied by professor. A couple profs asked specific questions about specific things I had written for the written portion. One didn't bring up anything I had written, just asked how I would have answered the essay questions I didn't choose to write on and asked about an important article that had recently been published. Another prof brought a text I had dealt with in a course a couple of years earlier and asked me some questions related to its interpretation because he (honest to god) wanted to know some of my thoughts about it. So, it might not hurt to think about the personalities of your profs and what your relationships with them are like.
The overall idea was for my profs to figure out the limits of what I knew. Questions kept being asked until I couldn't answer them, or at least until it revealed what my limits were. They were trying to make sure I seemed like a well-rounded junior scholar in my field. At times it was fun. Other times it really felt like the hot seat and like I'd be failed for not giving the correct answer. Hopefully, all your professors are on your side and wanting you to do well. Mine were, but I know that isn't always the case.
I don't know how your department is set up, but approval of my thesis proposal was done at the same time. So, there were questions about my project and all that jazz after I had passed my orals but during the same meeting. That might factor into your three hours and be prepared for it if it does. Someone in your department should at least be able to tell you if that will be covered or not.
Obviously, I can only talk in generalities about these things, but to me it helped to know that at some point I could say that I didn't know the answer and that was what they were looking for. We all have our limits. If we're good scholars, then we can be honest about where those are.
How do you feel you did on your written exams? Those were the ones that overwhelmed me. I felt a lot more confident with the orals. Be sure to figure out any mistakes you made in your written exams or any clarifications to what you wrote. But if you feel confident about how you did on the written exams, then the orals shouldn't be too bad.
Good luck!