How can I write file in SFTP

Summary:

Here is my integration: I am calling a BIP (csv output format) and fetching the output in chunks. Expected output can be >10mb thats why I am doing like this.

Now inside the while loop I have the file reference and I can write it in SFTP. But when the report is large, the while loop runs more than once and in that case multiple files are getting placed in SFTP.

I can move the SFTP write file outside the while loop but if I do so, I dont get the file reference.

How to design this?