53400: configuration_limit_exceeded

What does it mean?

The operation failed because a configuration limit was exceeded. The server rejected the request because of a defined limit (e.g. temp_file_limit, the number of replication slots or WAL senders).

Why does it happen?

Typical examples: a query's temporary file usage exceeding temp_file_limit ('temporary file size exceeds temp_file_limit'); all replication slots being in use ('all replication slots are in use', max_replication_slots); exceeding the max_wal_senders limit. Note: max_prepared_transactions exhaustion returns 53200, and prepared transactions being disabled (value 0) returns 55000.

How to fix it

The error message states which limit was exceeded. For temp_file_limit, optimize the query (use EXPLAIN ANALYZE to find sort/hash steps spilling to disk), increase work_mem at session level if needed, or raise the limit deliberately. If slots are exhausted, clean up unused slots after verifying their owners: SELECT slot_name, slot_type, active FROM pg_replication_slots; or increase max_replication_slots / max_wal_senders and restart the server.