Persistent middle tier components without logging

Enterprise applications need to be highly available and scalable. In the past, this has required "stateless" applications, which essentially require the application to manage its state explicitly by storing it in transactional resource managers. Despite "stateful" applications being more natural and hence easier to write and get correct, having the system manage this state automatically has been considered too difficult and too costly. The Phoenix/App system showed how to manage state in stateful applications transparently, by logging interactions between components, guaranteeing "exactly once" execution of the application. By introducing some minor restrictions on Phoenix/App components, no logging need be done for middle tier components, thus making it easy to provide both availability and scalability. Because there is no logging, the performance of failure free application executions is excellent.