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1. Message - transaction message (...FinishRequest for 2PC, ...PrepareResponse for 1PC)
   1. it is considered guaranteed that it's sent after all transaction DataRecords are written into WAL on sending node.it is considered received after all transaction DataRecords are written into WAL on receiving node. .
2. ChannelState - for single channel it's a set of messages that was sent (changed LocalState of sending node), but not received yet (hasn't changed LocalState of receiving node).
   1. In Ignite we can think that incoming ChannelState is represented by active transactions in PREPARING+ state (the Message might be sent by other nodes, but isn't received yet).
3. IncrementalSnapshot - on Ignite node it is represented with 2 WAL records (ConsistentCutStartRecord commits the WAL state, ConsistentCutFinishRecord describes the ChannelState). It guarantees that every node in cluster includes in the snapshot:
   1. transactions committed before ConsistentCutStartRecord and weren't included into ConsistentCutFinishRecord#after();
   2. transactions committed between ConsistentCutStartRecord and ConsistentCutFinishRecord and were included into ConsistentCutFinishRecord#before().
4. Marker - mark that piggy backs on the Message, and notifies a node about running snapshot.

   1. After IS start and before finish all PrepareRequest, FinishRequest are wrapper by ConsistentCutMarkerMessage instead of regular Message. This is done to notify target node ⁣⁣via communication channel about running IS.

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