There can be 1 to 8 concurrent database sessions (multi-DB mode), so that user specifications have to be available for each database session.
The following precedence rules apply for the user specifications:
1. If no CONNECT statement is specified for the database session in the application program, the user specifications are taken from the XUSER file.
2. If a database session is opened via a CONNECT statement, those user specifications are taken which are made in the CONNECT statement. Missing specifications are fetched from the corresponding XUSER parameter combination.
3. For the database session with the number 1, the user specifications can be overridden.
If the isolation level was set by means of the corresponding precompiler option, it can only be overridden by a runtime option.