Imported from previous forum
What is the purpose of tag 393 in security definition? I think security definition can be used to send tradable instruments to other party. If for example sending party has 200 future and 100 spread contracts, how this should be sent to the requesting party? My understanding is that tag 146 with a definition is used to specify underlytings. Then is it needed to send say 300 different security definition messages? How does other party knows when the messages have ended?
Thanks for help.