Oracle extending datafile during backup

Dear,

I am planning to set autoextend to ON on my datafiles, but I have concern what will happen with datafile/backup when backup of this file is running at the same time.oracle is trying to expand datafile. Can you point me to document/note where this situation is described.

I am running oracle 9.2.0.6 and 10.2.0.2 and BRTools version 6.40 or 7.00.

Regards,

Andrija