What memory management paradigm would you recommend, for an application like this? Let's say, a 1 hour game session generates ~100 GB of transient data, but onl

What memory management paradigm would you recommend, for an application like this? Let's say, a 1 hour game session generates ~100 GB of transient data, but only 100 MB is needed for what is currently within the camera's view at any one time. How do you keep track of which data is still important, and when do you release memory?