I all,
i try to implement a sevice to booking a room.
I must to deploiy it on jboss 3.2.7 and i use CMT

The problem is when 2 client A, B call at same time booking method:
1)A: call "booking" with big Collection, order by date, include booking for tomorrow
2) A: call "verifyAvaibleBooking(bookingVO)" and nobody booking for tomorrow
3) B: call "booking" with only booking for tomorrow
A: continues to verifyAvaibleBooking
4) B call "verifyAvaibleBooking(bookingVO)" and nobody booking for tomorrow and create a booking for tomorrow
5) A: terminate to verifyAvaibleBooking and create booking

At the end of this computation i have 2 booking for tomorrow on the same room!

This is my bookingBean:

/* @ejb.bean name="Booking" display-name="Name for Booking"
 * description="Description for Booking" jndi-name="ejb/Booking"
 * local-jndi-name = "ejb/BookingLocal" type="CMP" cmp-version="2.x"
 * view-type="local" primkey-field = "id"
 *
 */

public abstract class BookingBean implements EntityBean {
//every get method have this tag
 /**
 * Getter for CMP Field id
 *
 * @ejb.persistent-field
 * @ejb.interface-method view-type="local"
 *
 */
set...();
get...();
}

Now i have a Stateful antity bean to manage previews bean:

**
 * @ejb.bean name="ManageBooking" display-name="Name for ManageBooking"
 * description="Description for ManageBooking"
 * jndi-name="ejb/ManageBooking" type="Stateful" view-type="both"
 *
 * @ejb.resource-ref res-ref-name="jdbc/DefaultDS"
 * res-type="javax.sql.Datasource"
 * res-auth="Container"
 *
 *@jboss.resource-ref res-ref-name="jdbc/DefaultDS"
 * jndi-name="java:/DefaultDS"
 *
 * @jboss.container-configuration name="Standard Stateful SessionBean"
 *
 * @ejb.ejb-ref ejb-name="Booking" view-type="local" ref-name="ejb/BookingLocal"
 *
 * @ejb.ejb-ref ejb-name="User" view-type="local" ref-name="ejb/UserLocal"
 *
 * @ejb.ejb-ref ejb-name="ClassRoom" view-type="local"
 * ref-name="ejb/ClassRoomLocal"
 *
 * @ejb.ejb-ref ejb-name="Privilege" view-type="local"
 * ref-name="ejb/PrivilegeLocal"
 *
 * @ejb.ejb-ref ejb-name="MyConstraint" view-type="local"
 * ref-name="ejb/MyConstraintLocal"
 *
 */
public abstract class ManageBookingBean implements SessionBean{

 //Define some variable

 /**
 * Sets the session context
 * @param javax.ejb.SessionContext the new ctx value
 * @ejb.method setSessionContext
 **/
 public void setSessionContext(SessionContext ctx) throws EJBException,
 RemoteException {
 this.ctx = ctx;
 }

 /**
 * Unsets the session context
 * @param javax.ejb.SessionContext ctx value
 * @ejb.method unsetSessionContext
 */
 public void unsetSessionContext() {
 this.ctx=null;
 }

 /**
 * Default create method
 *
 * @throws CreateException
 * @ejb.create-method
 */
 public void ejbCreate() throws CreateException {
 try {
 userLocalHome = UserUtil.getLocalHome();
 classRoomLocalHome = ClassRoomUtil.getLocalHome();
 bookingLocalHome = BookingUtil.getLocalHome();
 constraintLocalHome = MyConstraintUtil.getLocalHome();
 } catch (NamingException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 }
 }


//There are some (not transaction) method

 /**
 * Business method
 *
 * @ejb.interface-method view-type = "remote"
 * @ejb.transaction type = "Required"
 */
 public String booking(Collection bookingVO) {
 .....
 }
}

This is a booking mathod:

 /**
 * Business method
 *
 * @ejb.interface-method view-type = "remote"
 * @ejb.transaction type = "Required"
 */
 public String booking(Collection bookingVO) {
 UserLocal userBean = null;
 ClassRoomLocal classRoomBean = null;
 Iterator iter;

 // Verifico la disponibilità
 Collection collBooking = verifyAvaibleBooking(bookingVO);

 if (collBooking.isEmpty()) {
 String tmp = computeConstraint(bookingVO);
 if (tmp.startsWith("Danied")) {
 return tmp;
 }
 iter = bookingVO.iterator();
 while (iter.hasNext()) {
 BookingValue booking = (BookingValue) iter.next();
 try {
 userBean = userLocalHome.findByPrimaryKey(booking.getUser()
 .getUserName());
 classRoomBean = classRoomLocalHome.findByPrimaryKey(booking
 .getClassRoom().getName());
 } catch (FinderException e1) {
 // TODO Auto-generated catch block
 e1.printStackTrace();
 }
 try {
 BookingLocal bookingBean = bookingLocalHome.create();
 bookingBean.setBookingValue(booking);
 bookingBean.setClassRoom(classRoomBean);
 bookingBean.setUser(userBean);
 } catch (CreateException e) {
 Costanti.debug("Errore nella creazione delle prenotazione");
 ctx.setRollbackOnly();
 }
 }
 } else {
 return Costanti.DANIED_BOOKING
 + "<br>Impossibile effettuare la prenotazione"
 + "<br>Ci sono altre prenotazioni negli stessi orari e nelle stesse aule";
 }
 return Costanti.OK_BOOKING + "<br>Prenotazione effettuata con successo";
 }

How can I make to resolve this problem?
I know that i can use UserTransaction but i'm know that CMT make this for me!
Someone can say me because i have this problem?
Thanks for your help everyone