Chicago Board of Options Exchange staff knew of problems with software hours before the glitch caused a half-day outage, but they thought they could fix them, the Wall Street Journal reported on Friday, citing people briefed on discussions.
CBOE officials have been looking into whether the exchange should have moved to its backup trading system instead of relying on staffers' ability to get the main system online, the report said.
A CBOE spokeswoman declined to provide details to Reuters about why CBOE did not switch to its backup system.
A software glitch shut down the CBOE for 3.5 hours on Thursday, preventing trading in options on two of the U.S. stock market's most closely watched indexes, the Standard & Poor's 500 Index and the CBOE Volatility Index.
The outage at CBOE on Thursday caused a 12 percent decline in overall U.S. index options trading volume from the day before, while single-stock options activity had a busier session as traders sought alternative venues to execute their positions, data showed on Friday.