(mysql.info) packet-too-large
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A.2.9 `Packet too large'
------------------------
A communication packet is a single SQL statement sent to the MySQL
server or a single row that is sent to the client.
The largest possible packet that can be transmitted to or from a MySQL
5.0 server or client is 1GB.
When a MySQL client or the `mysqld' server receives a packet bigger than
`max_allowed_packet' bytes, it issues a `Packet too large' error and
closes the connection. With some clients, you may also get a `Lost
connection to MySQL server during query' error if the communication
packet is too large.
Both the client and the server have their own `max_allowed_packet'
variable, so if you want to handle big packets, you must increase this
variable both in the client and in the server.
If you are using the `mysql' client program, its default
`max_allowed_packet' variable is 16MB. To set a larger value, start
`mysql' like this:
mysql> mysql --max_allowed_packet=32M
That sets the packet size to 32MB.
The server's default `max_allowed_packet' value is 1MB. You can
increase this if the server needs to handle big queries (for example,
if you are working with big `BLOB' columns). For example, to set the
variable to 16MB, start the server like this:
mysql> mysqld --max_allowed_packet=16M
You can also use an option file to set `max_allowed_packet'. For
example, to set the size for the server to 16MB, add the following
lines in an option file:
[mysqld]
max_allowed_packet=16M
It is safe to increase the value of this variable because the extra
memory is allocated only when needed. For example, `mysqld' allocates
more memory only when you issue a long query or when `mysqld' must
return a large result row. The small default value of the variable is a
precaution to catch incorrect packets between the client and server and
also to ensure that you do not run out of memory by using large packets
accidentally.
You can also get strange problems with large packets if you are using
large `BLOB' values but have not given `mysqld' access to enough memory
to handle the query. If you suspect this is the case, try adding
`ulimit -d 256000' to the beginning of the `mysqld_safe' script and
restarting `mysqld'.
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