The mysqld server stops reading the persisted system-variable file because the file size exceeds the internal maximum (1 MB by default).
MySQL Error 1340: ER_FPARSER_TOO_BIG_FILE appears when mysqld tries to load a persisted configuration file (mysqld-auto.cnf) larger than the 1 MB limit. Trim the file or delete and recreate it, then restart the server to resolve the issue.
Configuration file '%s' is too big
MySQL raises Error 1340 when the File Parser module reads the persisted system-variable file (mysqld-auto.cnf) at startup or during SET PERSIST and finds that its size exceeds the hardcoded limit of 1 MB. The server aborts file processing to avoid memory and performance issues.
The error halts the loading of persisted variables but the server still starts. Affected variables fall back to compiled defaults or values found in traditional option files (my.cnf).
The message surfaces mainly at server startup, after upgrades, or immediately after a SET PERSIST or SET PERSIST_ONLY statement that writes an oversized block to mysqld-auto.cnf. It can also appear on servers restored from backups where the persisted file grew unnoticed.
Ignoring the warning means expected dynamic configuration changes are silently skipped. Critical parameters such as max_connections or innodb_buffer_pool_size may revert, causing performance regression or even service outages. Cleaning the file restores predictable behaviour.
Repeated SET PERSIST statements append JSON objects to mysqld-auto.cnf until the combined size crosses 1 MB.
Storing large string values or many variables produces bloated JSON records, accelerating growth.
Unused persisted variables from staging or experiments remain in the file and inflate its size.
Editing mysqld-auto.cnf with an editor that adds comments or indentation can push the file over the limit.
The header of mysqld-auto.cnf is malformed, often due to manual edits.
The parser hit end of file while processing a comment, indicating a truncated JSON structure.
Attempted to persist a variable that cannot be saved to mysqld-auto.cnf.
No. The limit is compiled into MySQL. Keep the file small instead.
No. The server starts but ignores the oversized persisted file, so settings revert.
Yes, but back it up first. Missing file is recreated on next SET PERSIST.
Galaxy’s editor tracks SET PERSIST commands and warns when file size nears the limit, preventing the error before it occurs.
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