Your account seems confused. You say that you have defined a COBOL variable with PIC 9(5)V9(4) (USAGE IS DISPLAY is implied, so the data ought to be zoned decimal). Therefore, if the value is 8500000, it ought to be copied to DB2 as 850.0000. If, OTOH, the value is really 850, it would be copied as 0.0850. Neither is what you describe, so you are not describing what you are actually doing.
"You have sat too long for any good you have been doing lately ... Depart, I say; and let us have done with you. In the name of God, go!" -- what I say to a junior programmer at least once a day