All circuits are busy

It started innocently enough: At 2:25 p.m. on January 22, 1990, a New York City computer on the gigantic AT&T long-distance telephone network somehow came to believe it was overloaded and started to reject phone calls. When other computers on the network tried to pick up the slack for the supposedly overburdened New York City computer, they, too, exhibited the same weird symptoms. Eventually all 114 computers on the AT&T network were affected, and long-distance callers using the AT&T system all across the United States began to receive a busy signal or to hear the now famous "All circuits are busy" message. The problem continued for over nine hours, during which time AT&T lost between $60 million and $75 million in revenues. Companies who depend heavily on long-distance phone service for telemarketing were also big losers on this day. Some companies even sent their employees home because they could not make needed calls.

And what was the cause of this problem in the nation's largest long- distance network? Engineers traced the problem to a single logic error or "bug" in the software used to route calls on the AT&T network. This particular bug, like many others, arose during an effort to improve an existing software system. All of AT&T's computers use the same software, so all were affected by the same problem in logic.

While software designers are always working to ensure that software is bug-free, this is not always possible. A program like AT&T's faulty switching system can contain a million lines of code. Even when fault-tolerant computer systems attempt to reduce runaway system failure by having modules that check on each other, the entire system can go down if all modules simultaneously suffer the same malady.

A data base with a view

At the Car Product Development (CPD) Division of Ford Motor Company, over 150 end users can access multiple sources of data with a new mainframe computer interface called VIEW, which is an acronym for Virtual Interface Engineering Window. With VIEW, end users can access mainframe data base systems, such as DB2 and IMS and various types of flat files, to create necessary reports. The system especially benefits the information systems department, because it no longer has to create a second set of information for users to access. Now, users can go directly to the data bases they need, which saves system resources.

VIEW was written in four months, in the Focus 4GL, by systems analyst Wendy Balaka. It is menu driven and allows users to easily access data bases and create reports. For example, VIEW users created 12 reports in two months. It would have taken two years to create the reports with Ford's previous system, which required systems analysts to make repeated visits to clients to ask them what they want.

Users can store report formats in their personal libraries to create and print reports on the fly or overnight. VIEW also contains a global library, which lets users share their report formats with other users. The system is available only on the CPD mainframe, but there are plans to develop a PC equivalent so PC users can access data from a mainframe and download it to a spreadsheet or word processor.