Hello Jin Pan
The ABAP statements 'CREATE OBJECT' and 'CALL METHOD OF' use OLE automation on a (Windows) sapgui client. When you run a program in background it is executed directly on the SAP backend and there is no connection to a client computer. The SAP backend might even not run on Windows but on another operating system that doesn't support OLE automation. But even when it is these OLE statements only apply to client computers.
When you need to connect to a database in background you need another solution then OLE automation. Solutions like DBCON or UDConnect.
Regards Jack