how does rsync handle open/buisy files

I'm wondering if anyone that uses rsync hands open files or buisy files. does it copy them over or skip them. At the time of the night I plan to have rsync run no one should be here at the office but sometimes some files get left open or in a bisy state if there machine locks up an they do not tell me so that I can unflag them from the accounting software package so that the files they were working with in the account software gets updated to not being open/ locked. thanks for the info. jack