JPA Error when new entity is added without DropAndCreate

[buddhika.ari]

I am developing a J2EE application with JSF, EclipseLink2 as JPA installation and mySQL as the back-end database with Netbeans. Application works fine except when I add new attributes to existing entities, or create new Entities. If I select the dropandcreate option in Persistance.xml file, the application runs again without errors, but it deletes the whole data base with previous entries. When I go to production, I can not afford to lose data of the database when I add a new entity. Is there any way to overcome this. I tried to use a database schema, but could not figure how to do it. Thanks in advance