Adding to other replies...
2) Could you please specify step by step how to delete/fill setup table and the test you are suggesting to perform?
Use tCode: LBWG or execute the program RMCSBWSETUPDELETE --> enter application component 02 - purchasing in your case.
3) CMOD components just involve custom changes to datasources, don't they? I mean.. there is no reference to standard datasources extraction logic there. I'm thinking about debugging extractor to understand. Should I debbug MCEX_BW_LO_API function module, right?
yes you are right. CMOD component involves custom enhancements.
MCEX_BW_LO_API --> you can set up a break point in the Fm and goto RSA3 --> execute the data source in debugging mode. But difficult task to understand the SAP logic.
4) Cube 0PUR_C01 enhancement consists on adding some level of granularity. I need to add PO number and PO line item number from SCL and ITM data sources. Still no impact in 0PUR_C01 cube key figures?
Adding PO no and Line item from ITM and SCL extractor will not create any issue....
Instead of disturbing the current setup create a copy of the 0PUR_C01 info cube and and add the PO no and item to the custom cube and compare the data how it behaves.
Regards
KP