Hi I am trying to see what logic IB has for their OCA orders, and please let me know if this logic is correct or not .. when i create an OCA order (parent + child), then after a while i want to cancel the OCA order, this is what happens in the below order: 1. IB cancel all attached (child) orders in the OCA group. 2. IB send a cancellation order the the exchange for the parent order. wait a minute, does this mean that there is a possibility that IB can not cancel the parent order (if it has been filled already), while it has already canceled all the OCA child orders? unfortunately, it's true, which makes it impossible to use OCA for HFT.. let me know if such logic is right? shouldn't it seek the cancel in the exchange first, then cancel the OCA attached orders whom are still in the IB server (guaranteed to be canceled) ??? Thanks for any reply.