When APPEND is active, the system skips the file creation phase if the file already exists and moves the file pointer to the end of the document before writing the new data. Implementation Example
📌 The append functionality works best with 'ASC' (ASCII) and 'DAT' (Tab-delimited) file types. Using it with 'BIN' (Binary) requires precise control over the byte stream to avoid file corruption. It is generally not recommended for complex formats like Excel (.XLSX) files, as those are compressed XML structures that cannot be simply "appended" to at the binary level.
The GUI_DOWNLOAD function includes a specific importing parameter named APPEND. By default, this is set to space (false), meaning the function will overwrite any existing file with the same name. To enable appending, you must pass 'X' to this parameter.
Remember that GUI_DOWNLOAD requires an active GUI connection. It will not work in background jobs (SM37). For background processing, use OPEN DATASET with the FOR APPENDING addition on the application server.