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 to the user specifications:
1. If no connect statement for the database session is specified in the application program, the user specifications are taken from the XUSER file.
2. If a database session is opened via a connect statement, the user specifications made in the connect statement are taken. Missing specifications are fetched from the corresponding XUSER parameter combination.
3. The user specifications can be overridden for the database session with the number 1.
If the isolation level was set by means of the corresponding precompiler option, it can only be overridden by a runtime option.