Dictionaries
The dictionary registry controls how application messages are parsed and validated. Built-in dictionaries cover the supported FIX versions; tenant uploads add named alternatives without replacing those defaults.
Compatibility
- A FIX 4.2 session needs a FIX.4.2 dictionary.
- A FIX 4.4 session needs a FIX.4.4 dictionary.
- A FIXT.1.1 session uses the FIXT transport dictionary and a FIX.5.0SP2 application dictionary.
The Library table identifies a dictionary's name, BeginString, type, and upload time. It also shows affected sessions when a custom dictionary is in use.
Upload
Open Library → Dictionaries and upload the XML. The backend parses and validates the document before it becomes selectable. Use a distinct, stable name; changing the contents behind an existing name makes diagnosis and rollback harder.
Assign to a session
Select the dictionary in Sim Config and save. If the Library marks an affected session as needing a restart, restart that session to bind the changed dictionary in the engine.
Delete
Built-in dictionaries cannot be deleted. Before deleting a custom dictionary, check its usage count and move every dependent session to a compatible alternative. A name still referenced by a session is operational state, not dead content.
Verify
Send representative administrative and application messages, including repeating groups and custom fields. Check both acceptance and rejection: a dictionary that parses one happy-path order may still describe groups, field order, or required tags incorrectly.
Use the public FIX decoder and reference tools for quick inspection, but validate production session behaviour against the exact dictionary assigned to that session.
Updated 2026-09-08 · Edit on GitHub