Geographic Information Systems: An Introduction, 3rd Edition

18.7 Safekeeping and Security Routines

In many ways, computerized information is more vulnerable than conventional information. Errors in equipment, storage media, and computer programs, as well as user mistakes, can have serious consequences. Security routines are therefore necessary to guard against errors. As the collection of geographic information is very costly, damage to storage media (tapes, disks, etc.) can result in considerable financial loss. Moreover, as updating, access, and new data entry become more frequent, security must to be increased. On-line users can hardly be expected to wait several days while data are reconstructed following damage or an accident. Electrical outages or losses of data are expensive and time-consuming for both users and operating organizations. Security routines are therefore vital.

There are many causes of data loss. The storage medium may be damaged through misuse; equipment may fail; fire or other damage may occur. Data in daily use in a primary memory may be lost because of user errors, operative system errors, equipment failures, or electric power failures. Without prior warning, disk sectors or entire disks may become unreadable, or data stored on tapes may deteriorate.

Backup copies of disk files should be made periodically to minimize reconstruction work should file data be lost. A customary rule for systems in daily use is that all database changes must be automatically backed up daily from working disks onto tapes or tape cassettes. ...