NYSE mayhem traced to an employee who left a backup system running

More than 700 miles from Wall Street, the New York Stock Exchange’s backup data center on Cermak Road in Chicago is supposed to safeguard US markets, standing by at all hours in case disaster ever strikes the world’s largest venue for trading shares.
 

When markets are closed, it participates in a well-worn routine, with NYSE staffers turning on and off systems to ensure everything works. But heading into Tuesday, an NYSE employee failed to properly shut down Cermak’s disaster-recovery system — leading to a disaster.

That human error, described by people with direct knowledge of NYSE’s internal operations, is what triggered