(mysql.info.gz) Gone away

 
 A.2.8 `MySQL server has gone away'
 ----------------------------------
 
 This section also covers the related `Lost connection to server during
 query' error.
 
 The most common reason for the `MySQL server has gone away' error is
 that the server timed out and closed the connection.  In this case, you
 normally get one of the following error codes (which one you get is
 operating system-dependent):
 
 *Error Code*              *Description*
 `CR_SERVER_GONE_ERROR'    The client couldn't send a question to the
                           server.
 `CR_SERVER_LOST'          The client didn't get an error when writing to
                           the server, but it didn't get a full answer
                           (or any answer) to the question.
 
 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'.   Server system
 variables.
 
 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:
 
    * You (or the db administrator) has killed the running thread with a
      `KILL' statement or a `mysqladmin kill' command.
 
    * 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.
 
    * You got a timeout from the TCP/IP connection on the client side.
      This may happens 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.
 
    * 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).
 
    * 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 connection.
 
      In this case, even if the `reconnect' flag in the `MYSQL' structure
      is equal to 1, MySQL will 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 will in practice never time 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.  More information on setting the packet size is given
      in  Packet too large.
 
    * You will 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.
 
    * You may also see the `MySQL server has gone away' error if MySQL
      is started with the `--skip-networking' option.
 
    * 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.  
 Crashing.
 
 You can get more information about the lost connections by starting
 mysqld with the `--log-warnings=2' option.  This will log some of the
 disconnected errors in the `hostname.err' file.  Error log.
 
 If you want to create a bug report regarding this problem, be sure that
 you include the following information:
 
    * Indicate whether or not the MySQL server died. You can find
      information about this in the server error log.   Crashing.
 
    * If a specific query kills `mysqld' and the tables involved were
      checked with `CHECK TABLE' before you ran the query, can you
      provide a reproducible test case?   Reproduceable test case.
 
    * What is the value of the `wait_timeout' system variable in the
      MySQL server?  (`mysqladmin variables' gives you the value of this
      variable.)
 
    * Have you tried to run `mysqld' with the `--log' option to
      determine whether the problem query appears in the log?
 
 See also  Communication errors.
 
  Asking questions.
Info Catalog
(mysql.info.gz) Out of memory
(mysql.info.gz) Common errors
(mysql.info.gz) Packet too large
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