21.   The files are in numerical order.

22.   Serial files are the simplest form of file organisation.

23.   Sequential files are easy to use, they will support records of variable length and they use the backing storage media space efficiently.

24.   If the file is stored on disk, however, there are possible answers to the problem.

25.   Even then, if a file is very large, it may spread over a number of disks.

26.   A true direct access file is one where there is a direct relationship between the key field of a record and a unique address on disk.

27.   Next, a check is made that all referenced files are present.

28.   A high confidence that the offlined files are secure.

29.   It is preferable to take a good static BACKUP at least once a week with the process shutdown, so that the files are in a consistent condition.

30.   Whilst LIFESPAN will not modify anything in this directory except its own files, the upgrade instructions may assume that only LIFESPAN files are to be found here.