Today I had a discussion with a coworker about its implications for the files associated with a tablespaace when this is put into backup mode. The commented that the data files are not written during or while the tablespace is in backup mode. I believed remember that this was not implying the backup mode. Although I have a Oracle OCP and this is usually a typical exam question not remember exactly the question itself. I‘m getting old too fast. So nothing like reading the manual to refresh the memory (RTFM) .
According to the documentation in this case header data files are not updated until the backup mode is not removed, as is the tablespace or database. This is also to keep track of what you would have to implement recovery in case there was a problem.
HTH – Antonio NAVARRO