Perhaps I've not explained my "problem" clearly.
I know that declaring the bean read-only will prevent every data insert/update. But this is not my purpose. Certainly ejbStore is called whenever synchronization may be necessary.
I'm only trying to understand if JBoss has some performance tuning options to enhance on-memory works. For example you say "cmp2 engine checks to see if anything has changed": how is this performed? How could JBoss know if something has changed in the DB (without reading its data every time) if it is not the only process accessing it? If there were a way to ensure JBoss that it is the only process accessing the DB it should be able to work only in memory whenever it's possible, in the assumption that nobody is changing underlined data meanwhile. In every moment memory could be a partial mapping of the DB.
In a very simple way and some work this is implementable with BMP and a boolean field-status vector... but I was looking for a Container Managed solution.