What is the main difference between LS_UN_Sub and DG_CL_Sub?
In the DG data structure, is it mandatory to maintain LS_UN_Sub?
please check online help of SAP. If you would like to use EHS-DGP without DG filling you need not to maintain DG_CL_SUB nor LS_UN_SUB.
Topic is explained:
Dangerous Goods Basic Data (EHS-DGP-BD)
Mainly: on LS_UN_SUB the DG data is maintained and DG_CL_SUB specifcaiotns are used to combine data maintained on LS_UN_SU level.
Check may be: http://scn.sap.com/docs/DOC-41109
you will find more links related to that.
Always helpful is: http://help.sap.com/printdocu/core/print46c/en/Data/htm/english.htm