Hi Phani,
If you run DTP manually then the previous request/overlapping request will not be deleted automatically. It can only be done through process chains.
Where as If you are using infopackage to load the data directly to target (3.X data flow, without DTP) then you can set the overlapping request deletion status in the infopackage. In this case even if you run the Infopackage manually, over lapping request will be deleted automatically. And the same can be achieved through process chains also.
There is no such option available at DTP level, hence you have to go only with process chains to delete the overlapping requests automatically.
Regards,
Satya.