Hi Venkat
You should not have activated Classical PCA if you are using New GL.. New GL PCA is a much better functionality
Anyways, the reason for DUmmy PC is only that you did not assign the PC in the CO Object like Cost Center.. PC is always derived from Cost object. So, if the CO Object has no PC, the line item gets Dummy PC
There is a SAP note 702854 which offers steps to deactivate Classical PCA.. If you wish you can do that.. There is no harm as such in having Classical PCA, but New GL Is better
Br. Ajay M