The day after a major trading glitch at the New York Stock Exchange open, the NYSE has issued a statement on what happened: "The root cause was determined to be a manual error involving the Exchange's Disaster Recovery configuration at system start of day."
That's all they are saying. In plain words, it appears they tested a "disaster recovery configuration" that did not involve using the floor, and it did not reset.
Traders noted that both Designated Market Makers (DMMs) and floor brokers appear to have been frozen out of the order book that is used to build the opening print. No opening print was provided in dozens of big-name companies. "It was almost like trading opened without the participation of the floor," one observer who asked to remain anonymous told me.
What we know is that dozens of stocks opened at prices well above or below their prior day closing prices. Most were halted shortly after the open under rules designed to damp down excessive volatility, and most reopened five to 10 minutes after the open at prices much closer to Monday's closing prices. Many orders to buy and sell stocks did not make it into the order book that determines the opening price, and the opening auction print did not happen in those affected stocks.