Data security and contingency planning

In this chapter we will be concerned with the various ways in which CAD drawings can be accidentally destroyed and the procedures for preventing the loss. Any drawing costs far more than the medium holding it, whether paper, polyester film, disk or tape, on account of the labour invested in producing it. Losing a conventional drawing on film etc is not serious as it will most likely have been printed already so that a secondary master can be made from the print. A CAD drawing, on the other hand, cannot be reconstituted completely from a print on account of the precise but invisible numerical model lying behind it, of which the print is only a poor expression. There may even have been other data on invisible layers or in a parts listing which has not been printed at all. Consequently, a CAD drawing can only be stored as the computer file of binary numbers which it is.