因工作需要，需要导入一个200M左右的sql到user库
执行命令
mysql> use user Database changed mysql> source /tmp/user.sql 123 123导入的过程中出现MySQL server has gone away错误，数据导入失败。
错误信息如下：
ERROR 2006 (HY000): MySQL server has gone away ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 11 Current database: user ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 12 Current database: user ERROR 2006 (HY000): MySQL server has gone away ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 13 Current database: user开始以为是超时导致，因此调大了 connect_timeout 和 wait_timeout 的值。
重新执行后问题依旧。 解决方法：
查看资料，发现了 max_allowed_packet 参数， 官方解释是适当增大 max_allowed_packet 参数可以使client端到server端传递大数据时，系统能够分配更多的扩展内存来处理。
查看mysql max_allowed_packet的值
mysql> show global variables like 'max_allowed_packet'; +--------------------+---------+ | Variable_name | Value | +--------------------+---------+ | max_allowed_packet | 4194304 | +--------------------+---------+可以看到是4M，然后调大为256M(1024*1024*256)
mysql> set global max_allowed_packet=268435456; Query OK, 0 rows affected (0.00 sec) mysql> show global variables like 'max_allowed_packet'; +--------------------+-----------+ | Variable_name | Value | +--------------------+-----------+ | max_allowed_packet | 268435456 | +--------------------+-----------+ 1 row in set (0.00 sec)修改后执行导入，一切正常，解决问题。 注意： 使用set global命令修改 max_allowed_packet 的值，重启mysql后会失效，还原为默认值。
如果想重启后不还原，可以打开 my.cnf 文件，添加 max_allowed_packet = 256M 即可。
原文出处：http://blog.csdn.net/fdipzone/article/details/51974165#comments
