Entity Beans / Persistence - II
When the component is not in memory while its reference is active (meaning that it is not totally vanished from the persistent storage, like employee left the company), then the component is passive or in passive state.
The container swaps the components between active and passive states to utilize the server resources much like page swapping in virtual memory management.
During this process, container informs the component about its intention to change the state of the component via callback methods.
These callback methods give the component to a chance to take the necessary actions for state transition.