Messages can get out of order causing weird commit conditions. Client sends async messages during transaction and then commits. The commit message reaches servers that are not yet participants, but who become participants when they get their messages. Accept all new participants until commit. S a sends to S b sends to S c sends to S a .
Servers give superior role to first superior they have.
Server prepares, receives another request from unprepared server. Treat server as new participant. Remember aborted transaction until server has notified superior. Logging Circular storage. Composed of 512-byte blocks.