When LANSA connects to the database it records the information required to connect to the database. This is used at execution time to connect to the database. The most important information is the ODBC DSN, user id and password. There are many other parameters, most of them specific to a particular database. Please review the documentation that comes with your database for more information on these other parameters.
The ODBC DSN, user id and password may need to be changed in the executable environment. For example you may want to prompt for the userid and password every time the user connects, or use different DSNs for development, test and production systems. This can all be achieved using the DEFINE_DB_SERVER BIF, and optionally the CONNECT_SERVER BIF.