How To Fix SY421 - Specified comparison operator is not permitted

SAP Error Message - Details

• Message type: E = Error

• Message class: SY - ABAP/4 system messages

• Message number: 421

• Message text: Specified comparison operator is not permitted

What causes this issue?

You may only use one of the following comparison operators with
conditional watchpoints:

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

>, >=, =, <>, <, >=
The operator that you used here is not allowed.

System Response

How to fix this error?

Use one of the above comparison operators instead.
If you do not use a comparison operator, the debugger will stop
whenever the value changes.

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message SY421 - Specified comparison operator is not permitted ?

  The SAP error message SY421 ("Specified comparison operator is not permitted") typically occurs in ABAP programming when there is an issue with the use of comparison operators in a conditional statement. This error indicates that the operator used in the comparison is not valid or not allowed in the context where it is being used.
  Causes:
  
  Invalid Operator: The comparison operator used (e.g., =, <>, <, >, <=, >=) is not valid for the data types being compared.
  Data Type Mismatch: The operands being compared may not be compatible data types. For example, comparing a string with a numeric value.
  Syntax Error: There may be a syntax error in the conditional statement that leads to the use of an invalid operator.
  Logical Errors: Using operators in a way that does not make sense logically, such as trying to compare a table with a single value.
  
  Solutions:
  
  Check Operators: Ensure that the comparison operators used are valid for the data types being compared. For example, ensure that you are not using string comparison operators on numeric fields.
  Data Type Compatibility: Verify that the data types of the operands are compatible. If necessary, convert one of the operands to match the type of the other using appropriate conversion functions (e.g., CONCATENATE, TO_STRING, etc.).
  Review Syntax: Carefully review the syntax of the conditional statement to ensure that it is correctly formed. Look for misplaced parentheses or incorrect logical structures.
  Debugging: Use debugging tools to step through the code and identify the exact line where the error occurs. This can help pinpoint the specific comparison that is causing the issue.
  Consult Documentation: Refer to the ABAP documentation for the correct usage of comparison operators and examples of valid comparisons.
  
  Example:
  Here’s a simple example that could lead to this error:
  DATA: lv_value TYPE i,
        lv_string TYPE string.
  
  lv_value = 10.
  lv_string = '10'.
  
  IF lv_value = lv_string.  " This will cause SY421
    WRITE: 'Values are equal'.
  ENDIF.
  In this example, comparing an integer (lv_value) with a string (lv_string) will lead to the SY421 error. To fix it, you can convert the string to an integer:
  IF lv_value = lv_string.
    WRITE: 'Values are equal'.
  ENDIF.
  Conclusion:
  To resolve the SY421 error, carefully check the comparison operators and the data types involved in your conditional statements. Ensuring compatibility and correct syntax will help eliminate this error. If you continue to face issues, consider consulting with a colleague or referring to SAP community forums for additional insights.