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MySQL Troubleshooting Toolkit

MySQL Troubleshooting Toolkit

Diagnose slow queries and EXPLAIN plans, locks and deadlocks, replication lag, connection exhaustion, and InnoDB issues with prompts and runbooks.

Start troubleshooting Browse MySQL prompts

Top MySQL errors

Start with the most common production issues and troubleshooting paths.

ERROR 1038 (HY001)

Fix MySQL ERROR 1038 Out of sort memory: large ORDER BY/GROUP BY sorts, oversized sort_buffer_size, wide row sorts, and missing…

ERROR 1054 (42S22)

Fix MySQL ERROR 1054 Unknown column in field list: typos, missing migrations, wrong alias scope, GROUP BY on aliases, and reser…

ERROR 1153 (08S01)

Fix MySQL ERROR 1153 Got a packet bigger than max_allowed_packet: oversized BLOBs, large inserts, mysqldump restores, and clien…

ERROR 1194 (HY000)

Fix MySQL ERROR 1194 Table is marked as crashed: MyISAM corruption from crashes, full disk, or ungraceful shutdown. Repair with…

ERROR 1206 (HY000)

Fix MySQL ERROR 1206 total number of locks exceeds the lock table size: huge transactions, unindexed bulk DELETE/UPDATE, and un…

ERROR 1236 (HY000)

Fix MySQL replication ERROR 1236 Got fatal error 1236 from source: purged binlogs, missing GTIDs, corrupt binary logs, and binl…

ERROR 1366 (HY000)

Fix MySQL ERROR 1366 Incorrect string value: 4-byte emoji into utf8 columns, charset mismatches, and connection encoding issues…

ERROR 2003 (HY000)

Fix MySQL ERROR 2003 Can't connect to MySQL server over TCP: server down, wrong port, firewall, bind-address, and skip-networki…

Best MySQL prompts

Use these prompts to turn symptoms, logs, and config into a structured troubleshooting plan.

MySQL 5.7 to 8.0 Upgrade Readiness

Build a safe, staged plan to upgrade MySQL 5.7 to 8.0 (or MariaDB across majors): run the upgrade checker, surface removed/changed defaults, reserved words and collation pitfalls, and sequence the cutover with a rollback path.

MySQL CPU Spike & Query Load Triage

Triage a sudden MySQL/MariaDB CPU spike or load surge under live traffic: find the queries and threads burning CPU, separate a bad query plan from a thundering-herd or plan-flip, and stabilize without an outage.

MySQL Crash Recovery & InnoDB Corruption Triage

Triage a MySQL/MariaDB instance that won't start or crash-loops after an unclean shutdown or hardware fault: read the error log, decide on innodb_force_recovery levels, and recover data without making corruption worse.

MySQL Disk Full & Tablespace Reclaim

Recover a MySQL/MariaDB instance from a full data disk and reclaim space from bloated InnoDB tablespaces, binary logs, undo, and temp files without corrupting data or triggering more downtime.
All MySQL prompts

Free MySQL tool

Validate, troubleshoot, or analyze your configuration before production changes.

AI Incident Response Assistant

Paste a slow query, deadlock, or replication error, get a structured investigation.

Start triage

MySQL runbook

Use a repeatable checklist for production troubleshooting.

A first-response checklist for a struggling MySQL/MariaDB instance.

  1. 1 Check the process list and locks (SHOW FULL PROCESSLIST, SHOW ENGINE INNODB STATUS)
  2. 2 Review slow queries and their EXPLAIN plans
  3. 3 Inspect replication status and lag (SHOW REPLICA STATUS)
  4. 4 Check connections and limits (max_connections, Threads_connected)
  5. 5 Review the InnoDB buffer pool, deadlocks, and long transactions
Get the runbook checklist