I'm sure it's been brought up before,just can't recall the specifics. For example:A momo trader in and out on average every 30 minutes or so receives a partial fill on a buy order in a fast moving stock. It was routed on Island. IB I understand will keep seeking a fill until the order is completed. Being a babe in the woods I would conservatively think to cancel the rest of the order and ride with what was given. Otherwise I risk getting filled at my limit price on the way down. Not a comforting thought. Right or wrong? On the sell side a more dangerous partial also on the Island route with a fast moving stock. Unless I want to revert to investor,I have to get out! Should I rely on IB to find me a buyer? Or should I cancel the unfilled and put in a market order several levels below? Also,if one of you more experienced traders would take the time and tell me the precise mechanics of what you would do and how on the IB platform? BTW,in the auto routing of an order does IB charge for each attempt? Don't want to seem like a penny pincher but costs is what brings IB in the fold for their customers. Plus ,of course,fast executions. Thanks.