How To Fix OL400 - Function module &1 has references to data types that are not supported

OL400 - Overview

• Message type: E = Error

• Message class: OL - Workflow object types: Run-time system

• Message number: 400

• Message text: Function module &1 has references to data types that are not supported

What causes this issue?

The insert wizard for function modules does not support all types of
function module parameter. The following are not supported:
Parameters with generic types (for example TYPE C)
Parameters with the type TYPE

System Response

You can continue creating, but you will have to revise the method after
insertion.

How to fix this error?

The best way to proceed is as follows:
Continue the insertion of the method. When transferring parameters,
make a note of those to which you have not assigned a type.
Do not generate any implementation for the method, because this will
not usually be correct.
Revise the parameter types after the method has been inserted.
Now generate the implementation of the method by positioning the cursor
on the method and choosing the button 'Program'.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.

OL400 - Details

• The SAP error message OL400 indicates that a function module is referencing data types that are not supported. This typically occurs when there are issues with the data types used in the function module, such as unsupported structures, tables, or fields.
  Causes:
  
  Unsupported Data Types: The function module may be using data types that are not compatible with the current version of SAP or the specific context in which it is being executed.
  Custom Data Types: If the function module references custom data types or structures that are not properly defined or are incompatible, this error can occur.
  Changes in Data Dictionary: If there have been recent changes in the data dictionary (like changes to structures or tables), it may lead to inconsistencies.
  Transport Issues: If the function module was transported from one system to another, there may be missing dependencies or data types that are not available in the target system.
  
  Solutions:
  
  Check Data Types: Review