Hi Ralf,
Please have a look to table TRESC.
for reference please go through below link:
https://saptribalknowledge.wordpress.com/2012/04/04/find-allowed-namespace-for-table-or-view/
You can only reserve customer namespaces for tables and views to whichthe following applies:
- The delivery class of the table or view must be E or G.
- The table or view must be in a transportable package. Local, private
SAP program RDDKOR54 - Customer Namespace Reservations for Tables/Views
Hope this helps,
Thanks-
Abhishek