+…+ ?? ?1 + ?2+… + ??+…+ ??−1 (? < n − 1 < n) SAVEPOINT用于持久化各个子任务的执行状态 补偿行为：Forward Recovery/Backward Recovery/混合 执行路径 ?1 + ?2+… + ??+…+ ??(? < n) ?1 + ?2+… + ??+ ?? + ??−1 …+ ?1(? < n) ?1 + ?2+…

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Though sharding has solved problems such as performance, availability and single‐node backup and recovery, its distributed architecture has also introduced some new problems as acquiring profits. One problem sharding; • Support RC isolation level; • Rollback transaction according to undo log; • Support recovery committing transaction automatically after the service is down. Unsupported • Do not support other

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Though sharding has solved problems such as performance, availability and single‐node backup and recovery, its distributed architecture has also introduced some new problems as acquiring profits. One problem sending the commit command, all XAResource exceptions will be submitted again according to the recovery log to ensure the atomicity and high consistency. For example: XAResource1.prepare ## ack: yes

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will 4.2. Sharding 20 Apache ShardingSphere document, v5.0.0 be more uncontrollable with increasing Though sharding has solved problems such as performance, availability and single‐node backup and recovery, its distributed architecture has also introduced some new problems as acquiring profits. One problem sharding; • Support RC isolation level; • Rollback transaction according to undo log; • Support recovery committing transaction automatically after the service is down. Unsupported • Do not support other

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Though sharding has solved problems such as performance, availability and single‐node backup and recovery, its distributed architecture has also introduced some new problems as acquiring profits. One problem sharding; • Support RC isolation level; • Rollback transaction according to undo log; • Support recovery committing transaction automatically after the service is down. Unsupported • Do not support other

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Challenges Although data sharding solves problems regarding performance, availability, and backup recovery of single points, the distributed architecture has introduced new problems while gaining benefits sharding; • Support RC isolation level; • Rollback transaction according to undo log; • Support recovery committing transaction automatically after the service is down. Unsupported • Do not support other

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Challenges Although data sharding solves problems regarding performance, availability, and backup recovery of single points, the distributed architecture has introduced new problems while gaining benefits cross‐database transactions after sharding; • Rollback transaction according to undo log; • Support recovery committing transaction automatically after the service is down. Unsupported • Do not support isolation

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Challenges Although data sharding solves problems regarding performance, availability, and backup recovery of single points, the distributed architecture has introduced new problems while gaining benefits properties to the project’s class‐ path. See Atomikos’s official documentation for more details. Data Recovery xa_tx.log is generated in the logs directory of the project. This is the log required for recovering

thresh‐ old, DBA’s operation pressure will also increase. The time cost of data backup and data recovery will be more uncontrollable with increasing amount of data. Generally, it is a relatively reasonable Challenges Although data sharding solves problems regarding performance, availability, and backup recovery of single points, the distributed architecture has introduced new problems while gaining benefits properties to the project’s class‐ path. See Atomikos’s official documentation for more details. Data Recovery xa_tx.log is generated in the logs directory of the project. This is the log required for recovering

ShardingSphere document, v5.1.2 ├ ├ ├──status ├ ├ ├ ├──UUID ├ ├ ├ ├──.... ├ ├ ├──xa_recovery_id ├ ├ ├ ├──recovery_id ├ ├ ├ ├ ├──UUID ├ ├ ├ ├──.... ├ ├ ├──worker_id ├ ├ ├ ├──UUID ├ ├ ├ ├──.... ├