When a new record is inserted into the file, the DBMS must modify the indexes for each secondary-key field. For nonunique keys, it must make sure that the new record key value is in the values table; if it is, it adds the new record address to the appropriate entry in the occurrence table. If it is not, it must insert new entries in the values and occurrence tables. When a record is deleted, its address must be removed from the occurrence table. If no addresses remain in the occurrence table entry, the corresponding val-ues table entry must also be deleted.