Contrasts in large file memories for large-scale computers

Requirements for the use of very large files in digital computer systems for both scientific and business applications arise in a variety of circumstances. Certain characteristics of these applications tend to determine the type of file most suitable, where the file may contain well in excess of fifty million alphanumeric characters of information. These characteristics, some or all of which will be important in a particular application, include: 1. the upper and lower size limits of the file and the rate of change in total file size, 2. the volume of data which must be entered into and read from the file, either by other components of the mechanized system or by elements external to the mechanized system, 3. the speed with which each such reference must take place, 4. the average amount of data in one record and the variations in this amount, 5. the form of the original data and the desired form of information extracted from the file, 6. the control requirements dictated by particular kinds of files, especially the means of identification of records contained therein, and 7. the likelihood and implications of any unavailability, temporary or permanent, which may occur of information stored in the file.