Right up until the point when the last transaction to the main host is not processed, transactions will be received by the different sites. (Multi-Host File Sharing - MHFS)
When the heartbeat of the main host disappears, the other hosts will first recover the last transactions from the Comms processing units before resuming processing of normal traffic. I am no longer at the sharp end of this stuff (With a number of major airlines and demonstrating to clients), but the principles are the same. (Or should be).
IG