What happens if files are created/modified during backupexec backup operation?

Hi,

We use combination of Veeam / backup exec in our environment.

Veeam is used to do image backup of VMs, and backup exec copies these files to tape.

What happens if Veeam backup window and backup exec windows overlaps? 

If new file is created or exisitng file is modified(reverse incremental) during while backup exec backup is running, how does backup exec handle this?

Anyone has experience with this?

Thanks,

Mike