When you create a broker, you specify the user ID and password that are used to connect to the broker database. The user ID must be known to the database and must own the tables that are being accessed. When you create the database, ensure that you create them for the right user ID. DB2 authenticates the user ID using operating system user management, you do not have to define the user ID to DB2 itself.
When you issue the command that creates the broker, tables are created within the database to hold the information required.