SCCM 2007: data access tab on package: where is it for?

Hi,

I'm working mostly in SCCM 2012, now I have an SCCM 2007 in front of me. I'm a little confused on the DataAccess-tab. I read the Microsoft-article but it doesn't make me any wiser (http://technet.microsoft.com/en-us/library/bb693971.aspx). I made a new package but when I fill it in (yes, location is correct), it does not work, it does work when I don't fill it in.

Please clarify, why it is used, why you should or should not.

Jan Hoedt