I used to work at the trade desk of a moderate sized broker. When we would see our electronic orders start to back up and not deliver into the CBOE's system (known as RAES) a collective "Oh $ hit" would be yelled to each other, the next few hours would suck. Ask your broker what they do when an exchange is down. We had a back up destination for every option, so, if the CBOE went down we would modify a field in our system and all the CBOE order flow would shoot down to the ISE (if it traded on the ISE).