> 5.6.23在开启并行复制的时候，进行冷迁移后，start slave报错，set global slave_parallel_workers =0后可正常进行复制。 #### **说明** 已有从库并行复制配置：slave_parallel_workers = 4；通过停库拷贝datadir目录到目标机器，实现冷迁移，完成后目录机器start slave时报如下错误。 #### **具体的报错信息** Master_Log_File: mysql-bin.000283 Read_Master_Log_Pos: 715296037 Relay_Log_File: relay-log.000294 Relay_Log_Pos: 245347818 Relay_Master_Log_File: mysql-bin.000283 Slave_IO_Running: No Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: mysql.%,test.% Last_Errno: 1755 Last_Error: Cannot execute the current event group in the parallel mode. Encountered event Stop, relay-log name ./relay-log.000294, position 245347905 which prevents execution of this event group in parallel mode. Reason: possible malformed group of events from an old master. Skip_Counter: 0 Exec_Master_Log_Pos: 245347659 Relay_Log_Space: 715297197 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULL Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 1755 Last_SQL_Error: Cannot execute the current event group in the parallel mode. Encountered event Stop, relay-log name ./relay-log.000294, position 245347905 which prevents execution of this event group in parallel mode. Reason: possible malformed group of events from an old master. Replicate_Ignore_Server_Ids: Master_Server_Id: 2331597761 Master_UUID: 75f94423-e1c1-11e5-8da4-70e2840af125 Master_Info_File: /ssd/mysql/mysql_48284/var/master.info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Semi_Sync_Group: Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: 160311 15:54:17 Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: Executed_Gtid_Set: Auto_Position: 0 如上报错后，可stop slave后，将slave_parallel_workers设置为0，关闭并行复制,然后再start slave后，重新开启并行复制就没有问题。 可以参考下：http://bugs.mysql.com/bug.php?id=71495 ，之前的版本直接在日志里报的error。