Hi,
Did you try with DTP option instead of DSO name?
What are the connected data targets from this write optimized DSO? Do you have delta DTP request connecting this DSO to data targets upwards?
Can you write ABAP program and use it in process chain to delete data only ?
Class : CL_RSD_ODSO
You have to use FACTORY method with DSO name [DSO name can pass through variant] to initiate the instance and then use IF_RSD_DTP~DELETE_DATA to drop the data.
You can check if the data is dropped or not using IF_RSD_DTP_EXISTS_DATA method.
Please let me know if this helps you