Oracle.toplink.essentials.exceptions.DatabaseException - Error Code: -1

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="sifiscapPU" transaction-type="RESOURCE_LOCAL">
    <provider>oracle.toplink.essentials.PersistenceProvider</provider>
    <class>lib.database.Cargo</class>
    <properties>
      <property name="toplink.jdbc.url" value="jdbc:derby://localhost:1527/AtosPessoal"/>
      <property name="toplink.jdbc.user" value="root"/>
      <property name="toplink.jdbc.driver" value="org.apache.derby.jdbc.ClientDriver"/>
      <property name="toplink.jdbc.password" value="root"/>
    </properties>
  </persistence-unit>
</persistence>

//*
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package lib.database;

import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

/**
 *
 * @author welitoncb
 */
@Entity
@Table(name = "CARGO")
@NamedQueries({@NamedQuery(name = "Cargo.findByCodunidgestora", query = "SELECT c FROM Cargo c WHERE c.codunidgestora = :codunidgestora"), @NamedQuery(name = "Cargo.findByCodigocargo", query = "SELECT c FROM Cargo c WHERE c.codigocargo = :codigocargo"), @NamedQuery(name = "Cargo.findByNome", query = "SELECT c FROM Cargo c WHERE c.nome = :nome"), @NamedQuery(name = "Cargo.findByTipo", query = "SELECT c FROM Cargo c WHERE c.tipo = :tipo"), @NamedQuery(name = "Cargo.findByMes", query = "SELECT c FROM Cargo c WHERE c.mes = :mes"), @NamedQuery(name = "Cargo.findByAno", query = "SELECT c FROM Cargo c WHERE c.ano = :ano"), @NamedQuery(name = "Cargo.findByRemessa", query = "SELECT c FROM Cargo c WHERE c.remessa = :remessa"), @NamedQuery(name = "Cargo.findByExercicio", query = "SELECT c FROM Cargo c WHERE c.exercicio = :exercicio"), @NamedQuery(name = "Cargo.findByChave", query = "SELECT c FROM Cargo c WHERE c.chave = :chave")})
public class Cargo implements Serializable {
    private static final long serialVersionUID = 1L;
    @Column(name = "CODUNIDGESTORA")
    private String codunidgestora;
    @Id
    @Column(name = "CODIGOCARGO", nullable = false)
    private String codigocargo;
    @Column(name = "NOME")
    private String nome;
    @Column(name = "TIPO")
    private String tipo;
    @Column(name = "MES", nullable = false)
    private String mes;
    @Column(name = "ANO", nullable = false)
    private String ano;
    @Column(name = "REMESSA", nullable = false)
    private String remessa;
    @Column(name = "EXERCICIO", nullable = false)
    private String exercicio;
    @Column(name = "CHAVE", nullable = false)
    private String chave;

    public Cargo() {
    }

    public Cargo(String codigocargo) {
        this.codigocargo = codigocargo;
    }

    public Cargo(String codigocargo, String mes, String ano, String remessa, String exercicio, String chave) {
        this.codigocargo = codigocargo;
        this.mes = mes;
        this.ano = ano;
        this.remessa = remessa;
        this.exercicio = exercicio;
        this.chave = chave;
    }

Pacote lib.gui.
Arquivo CargoTabela.java

/*
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package lib.gui;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.swing.table.AbstractTableModel;
import lib.database.Cargo;

/**
 *
 * @author welitoncb
 */
public class CargoTabela extends AbstractTableModel{

    private  List listaIds;
    private ArrayList<Cargo> lista = new ArrayList();
    
    public CargoTabela(){
        EntityManagerFactory emf = javax.persistence.Persistence.createEntityManagerFactory("sifiscapPU");
        EntityManager em = emf.createEntityManager();
        
        listaIds = em.createQuery("SELECT c.codigocargo FROM Cargo c").getResultList();

        for(Iterator<String> it = listaIds.iterator(); it.hasNext();){
            String  elem = it.next();
            lista.add((Cargo) em.createNamedQuery("Cargo.findByCodigocargo").setParameter("codigocargo", elem).getSingleResult());
        }
        
        em.close();
    }
    public int getRowCount() {
        return lista.size();
    }

    public int getColumnCount() {
        return 5;
    }

    public Object getValueAt(int rowIndex, int columnIndex) {
       if(columnIndex == 0){
           return lista.get(rowIndex).getCodunidgestora();
       }else if(columnIndex == 1){
           return lista.get(rowIndex).getCodigocargo();
       }else if(columnIndex == 2){
           return lista.get(rowIndex).getNome();
       }else if(columnIndex == 4){
           return lista.get(rowIndex).getMes();
       }else if(columnIndex == 5){
           return lista.get(rowIndex).getTipo();
       }
       return null;
    }    
}