Electro-Therapie, Ou, Application Medicale Pratique De L'electricite Basee Sur De Nouveaux Procedes (French Edition)

The second one contained a list of the day's updates: products sold to customers and products delivered by suppliers. The computer read both input tapes and produced a new master inventory tape, as shown in Fig. 3-14. Fig. 3-14. Updating a master tape is fault tolerant. The great beauty of this scheme (although the people who had to live with it did not realize that) is that if a run failed for any reason, all the tapes could be rewound and the job restarted with no harm done. Primitive as it was, the old magnetic tape system had the all-or-nothing property of an atomic transaction. Now look at a modern banking application that updates an online data base in place. The customer calls up the bank using a PC with a modem with the intention of withdrawing money from one account and depositing it in another. The operation is performed in two steps: 1. Withdraw(amount, account1). 2. Deposit(amount, account2). If the telephone connection is broken after the first one but before the second one, the first account will have been debited but the second one will not have been credited ...»