Unique key violated when I am doing a delete. Because?

I have a problem that seems silly but I'm skating and I can not solve it. I have a legal application made in Java using JPA 2 with Spring, Spring Data, JSF, etc ... It works very well. The base I'm using is Oracle 10g.

Well now comes the problem, I have two tables. One related to the other. As follows:

Tabela: aplicacoes

 - id (pk);
 - nome;
 - usuario_acesso (unique key);
 - password;

Tabela: sessoes

 - id (pk);
 - token;
 - aplicacao_id (fk para tabela aplicacoes 1xN);
 - data_login;

Well, in this very simple example. I can have 1 application for N sessions. So far so good.

My problem starts when I try to delete an application that already has a session. Of course, I delete all sessions from that application before deleting the application, otherwise FK Violation would occur. But what happens here is that even though I delete all sessions pertaining to that application and then trying to delete the application a unique key violation !

Oras, why would this unique key no delete? It would make sense for this problem to occur when I insert a new record with a duplicate user name. But that's not the case.

The exception that occurs:

Caused by: java.sql.SQLIntegrityConstraintViolationException: ORA-00001: unique constraint (LOADERS_SCH.UK_9F63GD4XERQ7X8MNPKSKY69V) violated

    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:447)
    at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:396)
    at oracle.jdbc.driver.T4C8Oall.processError(T4C8Oall.java:951)
    at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:513)
    at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:227)
    at oracle.jdbc.driver.T4C8Oall.doOALL(T4C8Oall.java:531)
    at oracle.jdbc.driver.T4CPreparedStatement.doOall8(T4CPreparedStatement.java:208)
    at oracle.jdbc.driver.T4CPreparedStatement.executeForRows(T4CPreparedStatement.java:1046)
    at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1336)
    at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3613)
    at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:3694)
    at oracle.jdbc.driver.OraclePreparedStatementWrapper.executeUpdate(OraclePreparedStatementWrapper.java:1354)
    at org.jboss.jca.adapters.jdbc.WrappedPreparedStatement.executeUpdate(WrappedPreparedStatement.java:493)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:187) [hibernate-core-4.3.5.Final.jar:4.3.5.Final]
    ... 117 more

The error occurs precisely when I commit the transaction and not soon after sending the delete.

ISSUE: I'm adding the requested codes in the comments, plus some other things that might help with the answer.

ApplicationClientVO

@Entity
@Table(schema = "loaders_sch", name = "ws_aplicacoes_clientes")
public class AplicacaoClienteVO implements Serializable {

    private static final long serialVersionUID = 3401460653428856555L;

    @Id
    @SequenceGenerator(name = "id_seq_appcliente", sequenceName = "seq_appcliente", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_seq_appcliente")
    @Column(name = "id", nullable = false)
    private Long id;

    @Column(name = "nome_aplicacao", nullable = false, unique = true)
    private String nome;

    @Column(name = "usuario", nullable = false, unique = true)
    private String usuarioAcesso;

    @Column(name = "descricao", nullable = true)
    private String descricao;

    @Column(name = "password", nullable = false)
    private String password;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "ws_app_ws", joinColumns = { @JoinColumn(name = "app_id", referencedColumnName = "id") }, inverseJoinColumns = { @JoinColumn(name = "webservice_id", referencedColumnName = "id") })
    private Set<WebserviceVO> webservices;

    @Column(name = "ativo", nullable = false)
    private Boolean ativo;

    //Getters e Setters omitidos

SessãoVO

@Entity
@Table(schema = "loaders_sch", name = "ws_sessoes", indexes = {
        @Index(columnList = "token"),
        @Index(columnList = "app_cliente_id")
})
public class SessaoVO implements Serializable {

    private static final long serialVersionUID = -7578025167356770714L;

    @Id
    @SequenceGenerator(name = "id_seq_sessao", sequenceName = "seq_sessao", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "id_seq_sessao")
    @Column(name = "id", nullable = false)
    private Long id;

    @Column(name = "token", nullable = false, unique = true)
    private String authToken;

    @ManyToOne(targetEntity = AplicacaoClienteVO.class, fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "app_cliente_id", nullable = false)
    private AplicacaoClienteVO appCliente;

    @Column(name = "cliente_ip", nullable = false)
    private String ipCliente;

    @Column(name = "hostname", nullable = false)
    private String hostname;

    @Column(name = "porta", nullable = false)
    private String porta;

    @Column(name = "data_login", nullable = false)
    @Temporal(TemporalType.TIMESTAMP)
    private Calendar dataHoraLogin;

    @Column(name = "data_logout", nullable = true)
    @Temporal(TemporalType.TIMESTAMP)
    private Calendar dataHoraLogout;

    // Getters e setters omitidos

DAOs are interfaces that extend the Spring Data JpaRepository. So I do not have concrete DAOs implemented by me. I use Spring Data only. Below are the declarations of the methods that make the removals.

@Modifying
@Query("delete from SessaoVO sessao where sessao.appCliente = ?1")
void removeSessoesByCliente(AplicacaoClienteVO appCliente);

@Modifying
@Query("delete LogAcessoVO log where log.appCliente = ?1")
void removeLogsByApoCliente(AplicacaoClienteVO appCliente);

//Para remover a aplicação é usado o método default delete() do Spring Data.

Below is where the rule is applied and where the removal methods are called. Remembering that the error always occurs when committing the transaction.

ApplicationService

@Transactional(propagation = Propagation.REQUIRED, readOnly = false)
public void remover(AplicacaoClienteVO appCliente) throws ServiceException {
    if (appCliente != null && appCliente.getId() != null) {
        this.sessaoDAO.delete(this.sessaoDAO.findByAppCliente(appCliente));
        this.logService.removerLogsPorAplicacao(appCliente);
        this.appClienteDAO.delete(appCliente);
    }
}

The error constraint (UK_9F63GD4XERQ7X8MNPKSKY69V) refers to the session table.

Information in the user_constraint ( select * from user_constraints where constraint_name = 'UK_9F63GD4XERQ7X8MNPKSKY69V' ) table:

<ROW>
    <OWNER>LOADERS_SCH</OWNER>
    <CONSTRAINT_NAME>UK_9F63GD4XERQ7X8MNPKSKY69V</CONSTRAINT_NAME>
    <CONSTRAINT_TYPE>U</CONSTRAINT_TYPE>
    <TABLE_NAME>WS_APLICACOES_CLIENTES</TABLE_NAME>
    <SEARCH_CONDITION></SEARCH_CONDITION>
    <R_OWNER></R_OWNER>
    <R_CONSTRAINT_NAME></R_CONSTRAINT_NAME>
    <DELETE_RULE></DELETE_RULE>
    <STATUS>ENABLED</STATUS>
    <DEFERRABLE>NOT DEFERRABLE</DEFERRABLE>
    <DEFERRED>IMMEDIATE</DEFERRED>
    <VALIDATED>VALIDATED</VALIDATED>
    <GENERATED>USER NAME</GENERATED>
    <BAD></BAD>
    <RELY></RELY>
    <LAST_CHANGE>05/06/2014 16:53:04</LAST_CHANGE>
    <INDEX_OWNER>LOADERS_SCH</INDEX_OWNER>
    <INDEX_NAME>UK_9F63GD4XERQ7X8MNPKSKY69V</INDEX_NAME>
    <INVALID></INVALID>
    <VIEW_RELATED></VIEW_RELATED>
</ROW>