ODB no longer uses DPL layer of Berkeley DB, persistent classes have to
implement the Serializable interface, annotations are no longer used,
use transient modifier for variables that should not be persistent.
Entity reference errors will no longer occur, however it is better to
use ids if the entity that is being referenced is stored in the db too!
(or you will have two different objects). DB is cached for 5 minutes
then it will write its log/cache to disk, transactions are no longer
used.
Treeku