I had to change a username from mabri0 to svc_biztalk within the DB2 adapter. After I did this the DB2 adapter failed to connect anymore. I tried to test the connection using the Data Access Tool. It gave and error when trying to add the username and password, namely "The username is invalid or contains invalid characters". I removed the underscore and used a username like svcbiztalk and now the DB2 adapter connects.
Can anyone confirm that underscore is an invalid character for a DB2 username in a DB2 adapter connection string? I have to explain why this is so to the customer.