Software `doctor' prescribes remedies

At 4:00 a.m., the disk subsystem of a critical mainframe computer breaks down. Within a few minutes, the computer operator has reached the manufacturer's expert troubleshooter by phone at home. A short exchange yields the probable cause of the failure, and the operator begins to take corrective action. Scenes like this have been common for years, but they may become rare. With software techniques now being put into practice, no one need be awakened from a sound sleep for an expert consultation.