When running in an application server environment, the user account in which your application executes might be different from the account used for development. ODBC data sources set up as user data sources might, therefore, not be available. You will probably find it more convenient to set up data sources as system data sources on deployment systems. When a file-based data source is used, the database files must be accessible by the account used by the application server. When accessing the database, particularly if integrated security is used (that is, when the DBMS uses the same account number as the operating system), the default schema might be different from that used during development. This might well be what is intended, if different schema names are used for development and deployment. Alternatively, it might mean that tables are no longer visible to the application. It must either use explicit owner qualification, or execute a database-specific statement, which will select the correct schema to be the default.