If you change the database, you have to find the XA datasource of this db.
If you see in your persistence.xml, the property hibernate.hbm2ddl.auto=create indicates that each time the application is started the database will be recreated. This will make you loose all data each time you restart the application. If you set it to update, it will only update the changes (for example, if you add a column in hibernate, when you start the application the column will be added to the database.
Demian