2.17.2.6 Recovery of the Two Phase Commit Protocol

• Coordinator uses prepared to signal starting protocol, commit on signalling DoCommit and done to indicate end of protocol in recovery file.
• Participant uses uncertain to indicate that it has replied yes to commit request, and commited when it receives DoCommit.
• On recovery, coordinator aborts transactions which reach prepared, and resends DoCommit when in commit state but not done
• Participant requests decision from coordinator if in uncertain state, but not commited.