Yes it’s true. Prevayler is not a new idea. Mainframes have had transparent persistence for years. Only difference is that its handled at the operating system level. What applications see is a huge amount of addressable memory, what they don’t know is that some of that is actually stored on disk (or, given the context, on big rolls of magnetic tape). The operating system hides the various implementations of its memory storage behind a common interface. (Couldn’t resist that one).

So here’s an idea: how about using AOP to intercept and monitor object access patterns, moving them to and from disk-based storage as usage warrants. Seems to me like a natural extension to java’s generational garbage collection.