How To Fix FDT_EXPRESSIONS558 - Change of input table &1 by rule at position &2 may cause runtime errors

SAP Error Message - Details

• Message type: E = Error

• Message class: FDT_EXPRESSIONS - Formula & Derivation Tool: Expressions

• Message number: 558

• Message text: Change of input table &1 by rule at position &2 may cause runtime errors

What causes this issue?

In the current expression or rule, the system has determined a loop
expression with loop mode 'Foreach Entry'. This loop expression is
designed to iterate over the rows of table &v1&, thereby trying to
insert or delete entire table rows. This is a modeling decision for
which code generation is not possible because the resulting source code
would not pass the built-in syntax checks.

System Response

The object cannot be activated.

How to fix this error?

The constellation of a loop iterating over a table and at the same time
deleting or inserting rows is not necessarily an error. However, it may
be considered as a questionable approach that can easily lead to
unexpected problems, for example to an infinite loop.
To solve the problem, you may choose one of the following approaches:
Rather than using a loop expression, you may use a procedure call
expression associated with a class method. The method would contain the
loop mechanism, the table modifications, plus the checks needed to
ensure that the method can always terminate in a well-defined way.
You could create a copy of the table in question, assign this table copy
as a temporary variable to a ruleset, modify the table content as
required and finally copy the modified content back to the original
table.
If the use case you have in mind occurs frequently in your business, it
may be worth considering the definition of a custom expression type that
can handle all the requirements you may have. However, this approach
will certainly require the highest design time efforts.

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.

Smart SAP Assistant

• What is the cause and solution for SAP error message FDT_EXPRESSIONS558 - Change of input table &1 by rule at position &2 may cause runtime errors ?

  The SAP error message FDT_EXPRESSIONS558 indicates that there is a potential issue with a rule in the context of the Flexible Data Import (FDI) framework. This error typically arises when a rule attempts to modify an input table in a way that could lead to runtime errors, particularly when the rule is applied at a specific position in the processing sequence.
  Cause:
  The error is caused by the following scenarios:
  
  Modification of Input Tables: The rule is trying to change an input table (e.g., adding, removing, or altering fields) at a position where such changes could lead to inconsistencies or unexpected behavior during runtime.
  Incorrect Rule Logic: The logic defined in the rule may not be compatible with the structure or expected behavior of the input data.
  Data Dependencies: There may be dependencies between different rules or data elements that are not being respected, leading to potential conflicts.
  
  Solution:
  To resolve this error, consider the following steps:
  
  
  Review the Rule Logic: Check the logic of the rule that is causing the error. Ensure that it is correctly defined and does not attempt to modify the input table in a way that could lead to inconsistencies.
  
  
  Check Input Table Structure: Verify the structure of the input table being modified. Ensure that any changes made by the rule are valid and do not violate the expected schema.
  
  
  Adjust Rule Position: If possible, change the position of the rule in the processing sequence. This may help avoid conflicts with other rules or data processing steps.
  
  
  Test with Sample Data: Run tests with sample data to see if the error persists. This can help identify specific conditions under which the error occurs.
  
  
  Consult Documentation: Refer to SAP documentation or community forums for guidance on best practices when working with rules in the FDI framework.
  
  
  Seek Expert Help: If the issue persists, consider reaching out to SAP support or consulting with an expert who has experience with the FDI framework and rule definitions.
  
  
  Related Information:
  
  Flexible Data Import (FDI): A framework in SAP that allows for the import of data from various sources into SAP systems, often using rules to transform or validate the data during the import process.
  Error Handling: Understanding how to handle errors in the FDI framework is crucial for maintaining data integrity and ensuring successful data imports.
  SAP Community: Engaging with the SAP community can provide insights and solutions from other users who may have encountered similar issues.
  
  By following these steps, you should be able to identify the root cause of the error and implement a solution to resolve it.