Erro de Mapeamento - FK / PK

Galera, alguem saberia dizer o porque do erro do mapeamento? Tenho as seguintes tabelas abaixo:

create table STAETAPA
(
ID_STAETAPA NUMBER(10) not null,
ID_ETAPAPROPOSTA NUMBER(10) not null,
ID_STAFINAL NUMBER(10) not null,
ID_STACONTATO NUMBER(10) not null,
ID_SITUPROPOSTA NUMBER(10) not null,
ID_PROPOSTA NUMBER(10) not null,
STE_DTAGENDAINI DATE,
STE_DTAGENDAFIM VARCHAR2(5),
ID_USUARIO NUMBER(10) not null,
STE_DTCADASTRO DATE,
ID_PRIORIDADEAGENDA NUMBER(10),
ID_MIDIA NUMBER(10)
)
alter table STAETAPA
add constraint PK_STAETAPA primary key (ID_STAETAPA)

///////////////////

create table AGENDAPROPOSTADISCADOR
(
ID_STAETAPA NUMBER(10) not null,
AGDISC_DATA DATE not null
)
alter table AGENDAPROPOSTADISCADOR
add constraint PK_ID_STAETAPA primary key (ID_STAETAPA)

alter table AGENDAPROPOSTADISCADOR
add constraint REF_AGEPROPDISC_STAETAPA foreign key (ID_STAETAPA)
references STAETAPA (ID_STAETAPA);

Minhas classes estão mapeadas da seguinte forma:

//Classe AgendaPropostaDiscador
@Entity
public class AgendaPropostaDiscador {

@OneToOne(cascade = CascadeType.ALL)
@PrimaryKeyJoinColumn
private StaEtapa staEtapa;
		
@Column(name = "AGDISC_DATA")
private Date dataAgenda;

//getters e setters

}

//Classe StaEtapa
@Entity
public class StaEtapa {
@Id
@Column(name = “ID_STAETAPA”)
private Long idStaEtapa;
//outros atributos, getters e setters
}

Primeiramente, do “ponto de vista conceitual” sua chave estrangeira na tabela AGENDAPROPOSTADISCADOR não pode ser a chave primária desta tabela. Crie uma PK para a tabela em questão.

Segundo, suas classes estão fora do padrão EJB. Olhe um exemplo de mapeamento 1XN de Médico para Exame:

import java.io.Serializable;
import java.util.Collection;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;

@Entity
@Table(name = "medico")//aqui coloque o nome da tabela a qual a classe estará vinculada
public class Medico implements Serializable{

    @Id
    @SequenceGenerator(name = "medicoid", sequenceName = "medicoidseq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "medicoid")
    @Column(name = "id", nullable = false)
    private Long id;
    @Column(name = "nome", length = 40)
    private String nome;
    @Column(name = "crm", length = 40)
    private String crm;
    @OneToMany(mappedBy = "medico", fetch = FetchType.LAZY, targetEntity = Exame.class)
    @Cascade(org.hibernate.annotations.CascadeType.ALL)
    private Collection exames;

    public Medico() {
    }
   //getters e setters
}


import formatter.DateFormatter;
import formatter.DoubleFormatter;
import java.util.Date;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import org.hibernate.annotations.FetchMode;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.CascadeType;

@Entity
@Table(name = "exame")
public class Exame implements Serializable{

    @Id
    @SequenceGenerator(name = "lancexamid", sequenceName = "lancexamidseq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "lancexamid")
    @Column(name = "id", nullable = false)
    private Long id;    
    @ManyToOne(fetch = FetchType.EAGER, targetEntity = Medico.class)
    @JoinColumn(name = "idmed")
    @Cascade(CascadeType.SAVE_UPDATE)
    @Fetch(FetchMode.JOIN)
    private Medico medico;
    @Column(name = "descricao",length=410)
    private String descricao;
    @Column(name = "datapag")
    @Temporal(TemporalType.DATE)
    private Date dataPag;   
    @Temporal(TemporalType.DATE)
    @Column(name = "datalanc")
    private Date dataLanc;
    @Column(name = "valorexame")
    private Double valorExame;
    @Column(name = "valorpago")
    private Double valorPago;
    @Column(name = "valorreceber")
    private Double valorReceber;
    @Column(name = "pago",length=3)
    private String pago;