Despite the request by exchanges to postpone the start of CAT (Consolidated Audit Trail), SEC has said exchanges must begin providing trade data for what is likely to become one of the biggest databases ever conceived to track billions of orders per day.  It’s intended to help the SEC catch manipulators and diagnose the causes of market turmoil. It was first discussed before the infamous May 2010 Flash Crash, one of the worst routs in stock market history.