I know that Hibernate does not create a new column in the database that it uses for storing the version number. So how does it keep track of which objects are changed and which are not? Are there some hiden properties (in classes) and columns or tables (in database)? What does it compare on the persistent/transistent object and on the data row to see if it is changed? And what resourses does this take, how much does it cost?

Thanks in advance, ZarkoL