Upgrade ECC6 Upgrade ECC6 ERROR CX_SY_IMPORT_MISMATCH_ERROR

Hi guys..

Its been a 4 weeks that I have searching for the solution to get fix this error "Upgrade ECC6 ERROR CX_SY_IMPORT_MISMATCH_ERROR" in my customized report after getting upgrade from 4.6 to ecc6. but I haven't get done.I tried numerous method mentioned in different websites but couln't help me,

here is the part of my code which is given error at import statement.

tab5[] = tab4[].
clear tab4.
refresh tab4.
      import tab4 = tab4 from database  indx(st)  id indxkey
              to wa_indx.

please help me to get fix as I am new to sap development

     Thanks.