在用分库分表？
如果tm给rm发送commit命令时，其中一个rm没收到（网络故障等原因），结果会怎么样？
rm反馈提交成功时，其中一个rm没反馈或者反馈失败，然后，事务流程怎么走？
roll back
（参考In the second phase, the TM tells the RMs whether to commit or roll back. If all branches indicated when they were prepared that they will be able to commit, all branches are told to commit. If any branch indicated when it was prepared that it will not be able to commit, all branches are told to roll back.）

https://dev.mysql.com/doc/refman/5.7/en/xa.html
https://dev.mysql.com/doc/refman/5.7/en/xa-restrictions.html

谢谢wayne，可能没看清我的问题。感谢提供的资料。
XA transactions are not fully resilient to an unexpected halt with respect to the binary log. If there is an unexpected halt while the server is in the middle of executing an XA PREPARE, XA COMMIT, XA ROLLBACK, or XA COMMIT … ONE PHASE statement, the server might not be able to recover to a correct state, leaving the server and the binary log in an inconsistent state. In this situation, the binary log might either contain extra XA transactions that are not applied, or miss XA transactions that are applied. Also, if GTIDs are enabled, after recovery @@GLOBAL.GTID_EXECUTED might not correctly describe the transactions that have been applied. Note that if an unexpected halt occurs before XA PREPARE, between XA PREPARE and XA COMMIT (or XA ROLLBACK), or after XA COMMIT (or XA ROLLBACK), the server and binary log are correctly recovered and taken to a consistent state.
这段可能更能解答。
请问，是不是说xa处理不了第二阶段的异常？

我理解也是mysql xa处理不了，其他分布式数据库就不知道了~