public class TRCustomRepoImpl implements TRCustomRepository {
    @PersistenceContext
    private EntityManager em;
    @Override
    public String generateCareRefNum(String caseTyp, Integer seed) {
        // TODO Auto-generated method stub
        String caseRefNum = null;
        caseRefNum = (String) em.createNativeQuery("call case_ref_generator(?,?)")
        .setParameter(1, caseTyp).setParameter(2, seed).getSingleResult();

        return caseRefNum;
    }

}

org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions SQL Error: 6576, SQLState: 65000
rg.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions ORA-06576: not a valid function or procedure name