Does TRADE_RETCODE_DONE_PARTIAL mean IOC market order partially filled?

The documentation says: 

Only part of the request was completed

I just want to generate an alert if ever it happens, but are we 100% sure what the return code means?

Even though most of us probably never got that error code and can't test it in a demo or strategy tester, do we know if we would get this if a market order on IOC was partially filled because of a lack of liquidity?