The program mode is the mode in which the application server extracts data. When you generate an ABAP program, choose one of the following program modes:
File.
Extracts data to a staging file. The PowerCenter Integration Service accesses the file through FTP, SFTP, or NFS mount.
Stream.
Extracts data by using the RFC based on the type of connection you use to run the session.
If you use an SAP R/3 application connection, the PowerCenter Integration Service extracts data in stream mode by using the RFC protocol. RFC stream mode sessions use foreground processing.
If a mapping contains both hierarchies and tables, generate the ABAP program using file mode. The Designer does not generate ABAP if you choose stream mode for a mapping that contains hierarchies and tables.