I am currently working on a research project involving FIX market data snapshot messages. Because I do not have any real-world trading experience, I have some difficulties understanding the exact meaning of the messages and some fields. I already read the documentation but did not find a clear answer to my questions. I have the following questions about the example market data snapshot message posted below. Note: I replaced some values with characters.
The message has 44 repeating groups (each starting with 269). Does each repeating group represent the action of one trader, meaning in the message below one trader made a bid at a price of 1842 for 2 instruments at time x?
Is it true that repeating groups are created for efficiency reasons? Because otherwise for each repeating group a separate message would have to be sent with a new header and tail?
Thank you for your time.