Informix Error -568: Cannot reference an external database without logging.

Reasons / Common Causes

-568 fires when a statement in the current (logged) database references an external database that doesn't use transaction logging — per the official guidance, all databases participating in a single transaction must either all use logging or all not use it, and this statement tries to mix the two.

1. A cross-database reference from a logged database to an unlogged one, per the official guidance — the direct, only cause.
2. A staging/ETL database deliberately created without logging (for load performance) being referenced from a logged application database within the same transaction, without accounting for this restriction.
3. A database's logging mode changed after cross-database SQL was already written against it, turning previously valid cross-database statements into ones that now violate this rule.

Solutions / Resolution

1. Make the databases' logging modes consistent, per the official guidance's underlying requirement — either add logging to the external database, or work with it from an unlogged context instead.
2. If the external (unlogged) database's lack of logging is intentional (e.g. for staging/ETL performance), avoid referencing it directly from a logged database's transaction — move data between them via an unload/load step instead of an in-transaction cross-database reference.
3. Check a database's logging mode before writing cross-database SQL against it:

   SELECT is_logging FROM sysmaster:sysdatabases WHERE name = 'external_db';
   

Examples

The disallowed cross-database reference

DATABASE logged_app_db;  -- uses logging
SELECT * FROM unlogged_staging_db:raw_import;
-- -568: unlogged_staging_db doesn't use logging

Checking logging modes first

SELECT name, is_logging FROM sysmaster:sysdatabases
WHERE name IN ('logged_app_db', 'unlogged_staging_db');

Diagnostic Checks

1. Query sysmaster:sysdatabases for the is_logging status of both the current and the referenced external database, to confirm the mismatch before deciding how to resolve it.

Related Errors / Related Topics

• -569 — "Cannot reference an external database with logging." The mirror-image restriction: an unlogged current database referencing a logged external one.
• -570 — "Cannot reference an external ANSI database." The same family of cross-database mode consistency restrictions, for ANSI compliance rather than logging.

All databases in a single transaction must share the same logging mode — check sysmaster:sysdatabases.is_logging for both sides before writing cross-database SQL.