What is a good way to implement Reservation database EJB 3.0
@Entity
public class Reservation implements Serializable {
    ...
    private long startTime;
    private long endTime;
    private int  status;
    @ManyToOne
    private Customer theCustomer;   // record who made this reservation
    @ManyToOne
    private ReservableUnit theUnit; // record what this reservation is for
    ...
}

@Entity
public class ReservableUnit implements Serializable {

    private int numOfAvailableUnits;
    ...
    private int[][][] firstMonth = new int[31][24][2];
    ...
    private int[][][] fourthMonth = new int[31][24][2];
}

//status
public static final int AVAILABLE = 0;
public static final int BLOCKED   = 1;
public static final int RESERVED  = 2;