The NYSE glitch was caused by an employee who did not shut down the backup data center system on Cermak Road in Chicago.  On Tuesday, a system caused a temporary trading freeze. More: The backup data center was established to protect U.S. markets in case of a disaster. NYSE employees follow a routine of switching on and off systems to ensure the system works perfectly, and an employee left the backup center’s system running, causing a glitch. The error forced the exchange to cancel thousands of trades, the cost of which is yet to be determined. The glitch caused shares of companies like Walmart, Wells Fargo, Uber, and Exxon Mobil to swing as much as 25% in just a few seconds.