One-Cancels-All (OCA) Orders
An OCA order is actually a combination of separate orders that are worked in conjunction with one another in the marketplace.
To place these specific orders one must first open the Fixed Order Box form, accessed through the [O]rder button. There, enter the separate orders, making sure that each order has the OCA button checked.
All orders placed with a given Order Group name will form an OCA group. "OCA" is the default group name. You may enter your own order group name in the Order Group box (to the right of the OCA button).
You can transmit each order separately from the Fixed Order Box or after creating the orders, transmit them one after another while they are displayed on your TWS screen.
A. If, after transmission of the orders, any separate order within the OCA is canceled by the user, the remaining working order(s) will automatically be sent cancellation requests.
B. If any order in the group is partially executed, the contract size of the remaining order(s) will be adjusted downward in proportion to the fraction that was executed.
C. When any order in the OCA grouping is fully executed, the IB system will automatically issue a cancel request for the remaining order(s).
PLEASE NOTE: Because the OCA procedure is an automated process, Interactive Brokers cannot guarantee that requested cancellations and modifications will reach a specific exchange before an order has been executed.
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BTW the 'catch' with IB is that they are mainly an institutional broker (see their share of program trading) that allows retail clients access to the same system.