Dificuldade com persistencia de dados

@Entity
@Table(name = "membros", catalog = "glinksysdb", schema = "")
@NamedQueries({
    @NamedQuery(name = "Membros.findAll", query = "SELECT m FROM Membros m"),
    @NamedQuery(name = "Membros.findByMemCod", query = "SELECT m FROM Membros m WHERE m.memCod = :memCod"),
    @NamedQuery(name = "Membros.findByGCod", query = "SELECT m FROM Membros m WHERE m.gCod = :gCod"),
    @NamedQuery(name = "Membros.findByBairroCod", query = "SELECT m FROM Membros m WHERE m.bairroCod = :bairroCod"),
    @NamedQuery(name = "Membros.findByCidCod", query = "SELECT m FROM Membros m WHERE m.cidCod = :cidCod"),
    @NamedQuery(name = "Membros.findByDizCod", query = "SELECT m FROM Membros m WHERE m.dizCod = :dizCod"),
    @NamedQuery(name = "Membros.findByInscCod", query = "SELECT m FROM Membros m WHERE m.inscCod = :inscCod"),
    @NamedQuery(name = "Membros.findByRuaCod", query = "SELECT m FROM Membros m WHERE m.ruaCod = :ruaCod"),
    @NamedQuery(name = "Membros.findByMemNome", query = "SELECT m FROM Membros m WHERE m.memNome = :memNome"),
    @NamedQuery(name = "Membros.findByMemDataCad", query = "SELECT m FROM Membros m WHERE m.memDataCad = :memDataCad"),
    @NamedQuery(name = "Membros.findByMemEmail", query = "SELECT m FROM Membros m WHERE m.memEmail = :memEmail"),
    @NamedQuery(name = "Membros.findByMemMsn", query = "SELECT m FROM Membros m WHERE m.memMsn = :memMsn"),
    @NamedQuery(name = "Membros.findByMemDataNiver", query = "SELECT m FROM Membros m WHERE m.memDataNiver = :memDataNiver"),
    @NamedQuery(name = "Membros.findByProfCod", query = "SELECT m FROM Membros m WHERE m.profCod = :profCod"),
    @NamedQuery(name = "Membros.findByMemDataBat", query = "SELECT m FROM Membros m WHERE m.memDataBat = :memDataBat"),
    @NamedQuery(name = "Membros.findByCivilCod", query = "SELECT m FROM Membros m WHERE m.civilCod = :civilCod"),
    @NamedQuery(name = "Membros.findByMemComplemento", query = "SELECT m FROM Membros m WHERE m.memComplemento = :memComplemento"),
    @NamedQuery(name = "Membros.findByMemCelular", query = "SELECT m FROM Membros m WHERE m.memCelular = :memCelular"),
    @NamedQuery(name = "Membros.findByMemTelfixo", query = "SELECT m FROM Membros m WHERE m.memTelfixo = :memTelfixo"),
    @NamedQuery(name = "Membros.findByMemTelrec", query = "SELECT m FROM Membros m WHERE m.memTelrec = :memTelrec")})
public class Membros implements Serializable {
    @Transient
    private PropertyChangeSupport changeSupport = new PropertyChangeSupport(this);
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "MEM_COD")
    private Integer memCod;
    
    @JoinColumn(name = "G_COD", referencedColumnName= "G_COD")
    @ManyToOne
    private Membros gCod;