(from Day Trading Board)

NYSE says “problems with new software” led to yesterday’s outage
That’s a rare admission, as they usually pretend like they have no clue
Here’s what was learned from all the chatter yesterday:
1) They canceled ALL open orders… HOW MANY WAS THAT? 750,000 open orders were cancelled :o
2) These days, the NYSE only accounts for about 20% of all trades. :o 80% are executed “off board” on other exchanges and pools.
3) That final/last volume spike [5min] we always see at the close is MOC (market-on-close) orders from portfolio managers and mutual fund managers settling their day. We suspected that; now confirmed.
“Much of the trading on the NYSE happens at the end of the day, when portfolio managers put in orders designed to occur at the exact market close, to ensure end-of-day pricing…”
“60% of the NYSE SPX trades are MOC for funds and institutions” :o
Which is why they re-opened at 3:10 ET, to capture all their MOC orders which are an astonishing 60% of their daily SPX business…