When people start an enterprise application, one of the earliest questions is "how do we talk to the database". These days they may ask a slightly different question "what kind of database should we use - relational or one of these NOSQL databases?". But there's another question to consider: "should we use a database at all?"
One of the defining characteristics of enterprise applications is the need to store long term data, which naturally leads people to reach for a database. After all persisting data is one of the main things databases do. Using a memory image is a different route to persistence that doesn't involve a database.
The key element to a memory image is using event sourcing, which essentially means that every change to the application's state is captured in an event which is logged into a persistent store. Furthermore it means that you can rebuild the full application state by replaying these events. The events are then the primary persistence mechanism.