What is secondary storage area?
With Stateful Session Bean the passivation process of a bean it does saves the state of the bean in a secondary storage. The reason is because a stateful session bean do maintain the state between calls.
In order to do that, the container has to save that state somewere. It uses its own storage area, that could be memory or a cache or the disk, and it calls this "secondary storage area", since the database is considered to be the first storage area.