It is tricky to target persistent stores other than standard RDBMSes and OODBMSes. Entity beans need to be stored in a transactional system. Furthermore, this transactional system needs to be coordinated by JTS. In short, your database needs to be JTS-aware.

We do provide an SPI (service provider interface) to the container-managed persistence engine in the container. One can implement the interface for custom persistent stores and be able to have entity beans use that backend.