How To Fix FL389 - Only tables with flat line structure are allowed in RFC

FL389 - Overview

• Message type: E = Error

• Message class: FL - Function Builder messages

• Message number: 389

• Message text: Only tables with flat line structure are allowed in RFC

What causes this issue?

A structure with flat structure means that it contains only fields of
the data types ACCP, CHAR, CLNT, CUKY, CURR, DATS, DEC, FLTP, INT1,
INT2, INT4,LANG, NUMC, PREC, QUAN, RAW, TIMS, or UNIT.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message FL389 - Only tables with flat line structure are allowed in RFC ?

  The SAP error message FL389, which states "Only tables with flat line structure are allowed in RFC," typically occurs when you are trying to pass a table structure that is not flat (i.e., it contains nested structures or complex data types) to a Remote Function Call (RFC) in SAP. RFCs require that the data structures passed to them be flat, meaning they should not contain any nested tables or structures.
  
  Cause:
  
  Nested Structures: The table you are trying to pass contains nested structures or sub-tables.
  Complex Data Types: The data type of the table is not a simple flat structure, which is required for RFC calls.
  Incorrect Definition: The table may have been defined incorrectly in the ABAP Dictionary, leading to a non-flat structure.
  
  
  Solution:
  
  Flatten the Structure: Modify the table structure to ensure it is flat. This means removing any nested tables or structures and ensuring that all fields are at the same level.
  Use a