What is "partialFill" on Oanda's v20 API?

I am trying to write an entry order routine using Oanda's v20 API (a market if touched buy/sell with attached stop and take profit orders) and the returned JSON object on successfully placing the order shows


What is this? I can't find anything in the API documentation that either explains what this means and what the "default" implies in terms of how the order is affected. Furthermore, what are the alternative options to "default"?

I have received a reply from Oanda's help desk regarding this, which I quote below for forum members' information.

"The partialFill = DEFAULT value currently serves a limited purpose. It indicates that partial fill is possible if the order is marked as Immediate or Cancel (IOC). Beyond that, the value has no additional functionality at this time.

However, I would like to assure you that we are actively working on extending this feature. Shortly, we plan to release an update that will provide specific details on how orders can be partially filled on the trigger. This only applies when the Order's Time-In-Force is not FOK. Once it is released, you will be able to find all of the related information in our developer's guide."