Error: 2013 (CR_SERVER_LOST)
Message: Lost connection to MySQL server during query
Error: 2006 (CR_SERVER_GONE_ERROR)
Message: MySQL server has gone away
By default, the server closes the connection after eight hours if nothing has happened. You can change the time limit by setting the wait_timeout variable when you start mysqld.
If you have a script, you just have to issue the query again for the client to do an automatic reconnection. This assumes that you have automatic reconnection in the client enabled (which is the default for the mysql command-line client).
Some other common reasons for the MySQL server has gone away error are:
引起MySQL server has gone away错误的其它常见原因：
You (or the db administrator) has killed the running thread with a KILL statement or a mysqladmin kill command. 人为杀掉查询进程。
You tried to run a query after closing the connection to the server. This indicates a logic error in the application that should be corrected. 服务器关闭连接后，试图向服务器发送查询，这表明必须修改应用逻辑错误。
A client application running on a different host does not have the necessary privileges to connect to the MySQL server from that host. 客户端应用运行不同主机，连接至 mysql的主机没有必要的权限。
You got a timeout from the TCP/IP connection on the client side. This may happen if you have been using the commands: mysql_options(..., MYSQL_OPT_READ_TIMEOUT,...) or mysql_options(..., MYSQL_OPT_WRITE_TIMEOUT,...). In this case increasing the timeout may help solve the problem. 客户端TCP/IP连接超时，这可能是使用了mysql选项引起的，这种情况增加超时时间可以帮助解决问题。
You have encountered a timeout on the server side and the automatic reconnection in the client is disabled (the reconnect flag in the MYSQL structure is equal to 0). 服务器端连接超时和客户端自动重连被关闭
You are using a Windows client and the server had dropped the connection (probably because wait_timeout expired) before the command was issued.
The problem on Windows is that in some cases MySQL doesn't get an error from the OS when writing to the TCP/IP connection to the server, but instead gets the error when trying to read the answer from the connection.
Prior to MySQL 5.1.8, even if the reconnect flag in the MYSQL structure is equal to 1, MySQL does not automatically reconnect and re-issue the query as it doesn't know if the server did get the original query or not.
The solution to this is to either do a mysql_ping() on the connection if there has been a long time since the last query (this is what MyODBC does) or set wait_timeout on the mysqld server so high that it in practice never times out.
You can also get these errors if you send a query to the server that is incorrect or too large. If mysqld receives a packet that is too large or out of order, it assumes that something has gone wrong with the client and closes the connection. If you need big queries (for example, if you are working with big BLOB columns), you can increase the query limit by setting the server's max_allowed_packet variable, which has a default value of 1MB. You may also need to increase the maximum packet size on the client end.
An INSERT or REPLACE statement that inserts a great many rows can also cause these sorts of errors. Either one of these statements sends a single request to the server irrespective of the number of rows to be inserted; thus, you can often avoid the error by reducing the number of rows sent per INSERT or REPLACE.
INSERT or REPLACE语句插入大量的行也会引起这种错误。这些语句不考虑插入的行数而发送单一的请求至服务器。因此，减少插入的行数可以避免经常发生这种错误。
You also get a lost connection if you are sending a packet 16MB or larger if your client is older than 4.0.8 and your server is 4.0.8 and above, or the other way around.
It is also possible to see this error if host name lookups fail (for example, if the DNS server on which your server or network relies goes down). This is because MySQL is dependent on the host system for name resolution, but has no way of knowing whether it is working — from MySQL's point of view the problem is indistinguishable from any other network timeout.
You may also see the MySQL server has gone away error if MySQL is started with the --skip-networking option.
Another networking issue that can cause this error occurs if the MySQL port (default 3306) is blocked by your firewall, thus preventing any connections at all to the MySQL server.
You can also encounter this error with applications that fork child processes, all of which try to use the same connection to the MySQL server. This can be avoided by using a separate connection for each child process.
You have encountered a bug where the server died while executing the query.
You can check whether the MySQL server died and restarted by executing mysqladmin version and examining the server's uptime. If the client connection was broken because mysqld crashed and restarted, you should concentrate on finding the reason for the crash. Start by checking whether issuing the query again kills the server again.