What is the purpose of max_allowed_packet in MySQL?

max_allowed_packet is a parameter in MySQL server used to control the maximum size of an individual network data packet. Its purpose is to limit the maximum size of a single query or data packet sent from a client to the server.

When a client sends a query or packet, the MySQL server will divide it into multiple network data packets for transmission. If the size of a query or packet exceeds the setting value of max_allowed_packet, the server will reject receiving it and send an error message back to the client.

The default value for max_allowed_packet is 4MB, and you can change this value by modifying the MySQL configuration file or using the SET GLOBAL command in the MySQL command line.

This parameter is designed to prevent large queries or data packets in the network from consuming excessive resources, thus protecting the stability and performance of the server. It also helps prevent certain malicious attacks, such as overwhelming server resources by sending a large number of large queries or data packets.