Thank you Swati and Athreya
"This error was coming from PO_UNIT, failure".
In the data the value to PO_UNIT (MARA-BSTME) was passed without conversion.So it was throwing error.
wa_clientdata-po_unit = wa_mara-bstme<<<<< throwing error
I used the FM
call function 'CONVERSION_EXIT_CUNIT_INPUT'
exporting
input = wa_mara-bstme
language = sy-langu
importing
output = wa_clientdata-po_unit.
And now "NO ERROR"
.
Regards,
Lakshmi