Global transfer routine and DTP filter debug

Hi,

1.) Can any one explain me on what is Global tranfer routine?

2.) I have DTP filter with routine, now i want to keep beakpoint and debug this filter routine.

After double clicking DTP, in menu Extras -> Generated program filter checked ABAP code, here i am not getting DTP filter routine.

I have doubt is it possible to keep break points without writing ABAP code(BREAK-PONT.).

Thanks,

Manjunatha