MySQL raises error 2020 when a packet sent or received is larger than the max_allowed_packet size set on the client or server.
MySQL Error 2020: CR_NET_PACKET_TOO_LARGE happens when the client or server tries to transfer a packet exceeding max_allowed_packet. Increase max_allowed_packet on both client and server, or break the data into smaller chunks, to resolve the issue.
Got packet bigger than 'max_allowed_packet' bytes
MySQL returns the message "Got packet bigger than 'max_allowed_packet' bytes" when either the client or server attempts to send a data packet larger than the configured max_allowed_packet limit. The error originates in the MySQL client library and is labeled CR_NET_PACKET_TOO_LARGE, error code 2020.
The packet can be a query, result set, BLOB, or bulk INSERT. When its size exceeds the limit, the connection closes and the operation fails.
Fixing the limit or shrinking the data restores normal operation and prevents data loss.
The most common trigger is uploading or retrieving large BLOB, TEXT, or JSON documents that surpass the default 16 MB limit in MySQL 5.7+ or 4 MB in older versions. Large multi-row INSERT statements and SELECT * queries on wide tables can also create oversized packets.
Mismatched client and server settings intensify the problem.
If the client sets max_allowed_packet lower than the server, a big result set may reach the client limit first and raise error 2020 even though the server accepted it.
Increase max_allowed_packet on both the client and server to a value larger than the expected packet size. Restart the server after changing my.cnf or my.ini.
For session-level adjustments, use SET GLOBAL or SET SESSION statements and reconnect affected sessions.
If raising the limit is impossible, split large data into smaller chunks. Use chunked INSERT, LIMIT/OFFSET pagination for SELECT, or send BLOBs in pieces with LOAD DATA LOCAL or application-level streaming APIs.
Bulk loading CSV files often fails because the entire file is read into one packet. Use --local-infile with smaller batch sizes or increase the packet limit temporarily.
Export tools like mysqldump may also need --max_allowed_packet to match server settings.
Replicated environments require identical max_allowed_packet on master and replicas. Set the same value in every my.cnf to avoid replication lag or failure when large rows replicate.
Audit BLOB and TEXT sizes before inserting. Compress or shard objects that grow beyond tens of megabytes.
Configure conservative defaults like 64 MB and monitor packet statistics in PERFORMANCE_SCHEMA and the status variable Bytes_received.
Automate threshold alerts with tools such as pmacct or Prometheus exporters. Continuous monitoring helps catch oversized queries before they hit production connections.
Error 1153 ER_NET_PACKET_TOO_LARGE appears on the server side when the incoming packet exceeds the server limit. Unlike 2020, it is generated by the server thread.
The fix is identical: raise max_allowed_packet or shrink the data.
Error 1236 replication relay log read failure also surfaces when a slave encounters a packet larger than its configured limit. Setting consistent limits across all nodes prevents it.
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Inserting or selecting BLOB, TEXT, or JSON fields larger than the default 16 MB packet size immediately breaches the limit.
Applications that concatenate thousands of rows into one INSERT can create a single packet bigger than max_allowed_packet.
If the client has a smaller max_allowed_packet value than the server, large result sets fail on the client side with error 2020.
mysqldump, mysqlimport, or LOAD DATA operations may allocate buffers larger than allowed and trigger the error during transfer.
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In MySQL 8.0 the hard cap is 1 GB. Set a value that balances memory use and legitimate data size, typically 64-256 MB.
A restart is required when you modify my.cnf. Using SET GLOBAL applies immediately, but existing sessions must reconnect to inherit the new value.
If the client-side limit is lower than the server limit, the client fails first. Align both values to the higher setting.
Yes. Galaxy flags large result sets in the editor and suggests raising max_allowed_packet or adding LIMIT clauses before execution, reducing the chance of hitting error 2020.
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