Today I had my first execution of listed stock on ARCA. There was 100 shares offered at the time I send in 200 share limit order at ask price, figure I'll get a partial fill and cancel the rest 100 immediately after 100 is filled. The funny thing is after my 100 shares were filled, I tried to cancel the rest and cancel was pended for a long while, just like when I cancel my order sent to AMEX, and filled a little bit later. In AMEX case I understand that they hold your order. Since ARCA is electronic, I don't understand why this can happen. Anyone knows why?
The remainder of your order was rerouted by ARCA to SuperDOT (NYSE) or possibly a regional exchange or Nasdaq Intermarket market maker if they happened to quote a price superior to NYSE.