What is the advantage of puttting an Entity Bean instance from the "Ready State" to "Pooled state"?
This mean that the instances do represent entity beans, but they can be used only for serving Home methods (create or findBy), since those methods do not relay on the specific values of the bean. All these instances are, in fact, exactly the same, so, they do not have meaningful state.
Jon Thorarinsson has also added:
It can be looked at it this way:
If no client is using an entity bean of a particular type there is no need for cachig it (the data is persisted in the database).
Therefore, in such cases, the container will, after some time, move the entity bean from the "Ready State" to the "Pooled state" to save memory.
Then, to save additional memory, the container may begin moving entity beans from the "Pooled State" to the "Does Not Exist State", because even though the bean's cache has been cleared, the bean still takes up some memory just being in the "Pooled State".