EC
1203
MySQLERRORCommonConnectionHIGH confidence

User has exceeded the max_user_connections resource

Production Risk

HIGH — users are locked out while the limit is exceeded.

What this means

Error 1203 (SQLSTATE 42000) is returned when a specific user account has reached the max_user_connections limit — either the global setting or a per-user resource limit set via GRANT. Unlike error 1040 which limits total server connections, 1203 is per-user.

Why it happens
  1. 1The user account has a MAX_USER_CONNECTIONS resource limit set via ALTER USER or GRANT
  2. 2The global max_user_connections variable is non-zero and the user has reached it
  3. 3Connection leaks in the application are exhausting the per-user slot
How to reproduce

A user exceeds their per-user connection limit.

trigger — this will error
trigger — this will error
-- Check per-user limit:
SELECT user, max_user_connections FROM mysql.user WHERE user = 'appuser';

expected output

ERROR 1203 (42000): User appuser already has more than 'max_user_connections' active connections

Fix 1

Increase or remove the per-user connection limit

WHEN When the limit is artificially low for the workload.

Increase or remove the per-user connection limit
-- Remove per-user limit:
ALTER USER 'appuser'@'localhost' WITH MAX_USER_CONNECTIONS 0;
FLUSH PRIVILEGES;

-- Or raise it:
ALTER USER 'appuser'@'localhost' WITH MAX_USER_CONNECTIONS 50;

Why this works

Setting MAX_USER_CONNECTIONS to 0 means no per-user limit; the global max_connections limit still applies.

Fix 2

Fix connection leaks in the application

WHEN When connections are not being returned to the pool.

Fix connection leaks in the application
-- Identify all connections from this user:
SELECT * FROM information_schema.PROCESSLIST WHERE USER = 'appuser';

Why this works

Use try-with-resources or connection pool management to guarantee connections are closed after use.

Sources
Official documentation ↗

MariaDB Server error code 1203 / ER_TOO_MANY_USER_CONNECTIONS

MariaDB ALTER USER Resource Limits ↗

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