sequential list can be readily stored as sequential files. this solution, however, is not generally supported by DBMS products because sequentially reading a file is a slow process. further, sequential files can not be updated in the middle without rewriting the entire file. also, maintaining several orders by keeping multiple copies of the same sequential list is usually not effective because the duplicated sequential list can create data integrity problems. fortunately, other data structures allow us to process records in different orders and do not require the duplication of data. these data structures include linked lists and indexes.