insert, update, write to disk, commit. That’s it, right? Well, yes and no. Well, no. Oracle is complex (you might have noticed) and it has a lot of mechanisms to ensure data integrity when you make changes. I hope I can explain what’s going on, so you can understand just how much work Oracle is doing to ensure the data you are reading and writing is correct, and showing how Oracle avoids doing work unless it really has to. I’m sorry, but this will involve showing you some block internals.