getting
EXCEPTION:
ORA-00904: "ELT": invalid identifier

while persisting a SET refrence to associated object.
example:
1)---------------:classes:---------
class 1:
public class Student implements Serializable {
Integer id;
String firstName;
String lastName;
Set courses;
}
class 2:
public class Courses implements Serializable {
private int id;
private String course_name;
private Set students;
}
2)-------tables----------
table 1:
Student(studentId PK,firstName,lastName)
table 2:
Courses(courseId PK,course_name)
table 3:
StudentCourses(studentId FK STUDENT(studentId ),courseId FK COURSES(courseId),PK(studentId,courseId));

3)------------saving----------
Courses crs=new Courses();
Student s=new Student();
s.setId(10);
s.setFirstName("ABC");
s.setLastName("XYZ");

crs.setId(10);
crs.setCourse_name("J2EE");
Set set2=new TreeSet();
set2.add(s);
c.setStudents(set2);
Save(c); //exception
/////////////
4)-----------exception-------------------------------
Hibernate operation: could not insert collection: [Course.studen#10]; bad SQL grammar []; nested exception is java.sql.SQLException: ORA-00904: "ELT": invalid identifier

Sorry, what is c? Is it a typo and you meant crs?

Do you have mapping files?