The max.allowed.packet size limits the size of query packet from client. It may be specified at both client and server side. JDBC clients may need to pass “sessionVariables=maxAllowedPacket=…” during connection setup since the driver may not support changing session properties once the session has been established.See also this post. On server side, mysql --max_allowed_packet=32M to set the property and show variables like 'max_allowed_packet to query it.

Note that max allowed packet property is distinct from the fetch size property, which limits the number of rows fetched from the database.