Rsync 2.6.5 --remove-sent-files

Dear all,

Can somebody explain me a bit more about the option
"--remove-sent-files", something a bit more detailed than in the docs?

The reason is that I'm currently building an app that need to tsf files
between two server. But I've to make sure that files tsf are not sent a
second time. The destination manipulate files asynchronously and delete
the file when processed. Which means I've no way to count on the fact
that destination will offer me a list of file already present.

I've used the option which works well when the rsync complete with a
status 0. But in case the net connection drops, I've a timeout and
already sent files are not deleted from source.

I was thinking that, the option was deleting the files during transfer
and not at the end.

Can someone confirm this?

Thx to all.