SAP Message RE900 - Invalid function code &

Diagnosis
The mode for the data transfer in the interface was not valid. Thevalid values are : I Insert
C Change budget address:
Fields: FIPOS FISTL GEBER
REFRESERV REFRESPOS
REFPRECOM REFPREPOS
KRTYP KRIT
M Modify: all other fields

System Response
Program terminates

Procedure
Check and correct the mode, then start the program again.