Question: how to debug qrfc in sap?
Answer: Go to the program 'ZREPORT' and go to the CALL FUNCTION 'ZFUNCTIOn' IN BACKGROUND TASK .
Keep breakpoint in 'ZREPORT' just before the CALL FUNCTION start .
when you reach the breakpoint, Go to menu -- > Settings -> Display/Change debugger settings -> select the flag "tRFC (In Background Task): Block Sending".