If you check out the SAP Help, the SY-SUBRC = 8 means the app server was unable to open the file.
In your dump does it mention the name of the class based exception that was raised?
http://help.sap.com/abapdocu_702/en/abapopen_dataset.htm
For test purposes, you can set it to CX_ROOT and see what comes up. Then change it to something more appropriate. CX_DYNAMIC_CHECK will only be raised for catchable exceptions caused during runtime.
Hope that helps...