How To Fix W8130 - Table action "Append" not possible when reading an element

SAP Error Message - Details

• Message type: E = Error

• Message class: W8 - Workflow: Expressions, data flow

• Message number: 130

• Message text: Table action "Append" not possible when reading an element

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• What is the cause and solution for SAP error message W8130 - Table action "Append" not possible when reading an element ?

  Certainly! Here's a detailed explanation for the SAP error message:
  
  SAP Error Message:
  W8130 Table action "Append" not possible when reading an element
  
  Cause:
  This warning occurs when an ABAP program tries to use the APPEND statement on an internal table while reading or looping through the same table. Specifically, the error arises if you attempt to append a new line to an internal table during a READ TABLE or LOOP AT operation on that same table.
  In ABAP, modifying an internal table (like appending a new row) while simultaneously reading or looping over it is not allowed because it can lead to inconsistent or unpredictable behavior.
  
  Explanation:
  
  APPEND adds a new line to the end of an internal table.
  READ TABLE or LOOP AT is used to read or iterate over the internal table.
  If you try to append a new line to the table during the read or loop, the system raises this warning to prevent data inconsistency.
  
  
  Example that causes the warning:
  DATA: lt_table TYPE TABLE OF string,
        lv_line  TYPE string.
  
  APPEND 'Line 1' TO lt_table.
  APPEND 'Line 2' TO lt_table.
  
  LOOP AT lt_table INTO lv_line.
    IF lv_line = 'Line 1'.
      APPEND 'New Line' TO lt_table. " This causes W8130 warning
    ENDIF.
  ENDLOOP.
  
  Solution:
  To avoid this warning, do not modify (append, insert, delete) the internal table while reading or looping over it. Instead, use one of the following approaches:
  
  Collect new entries in a separate internal table and append after the loop:
  
  DATA: lt_table TYPE TABLE OF string,
        lt_new   TYPE TABLE OF string,
        lv_line  TYPE string.
  
  APPEND 'Line 1' TO lt_table.
  APPEND 'Line 2' TO lt_table.
  
  LOOP AT lt_table INTO lv_line.
    IF lv_line = 'Line 1'.
      APPEND 'New Line' TO lt_new.
    ENDIF.
  ENDLOOP.
  
  " Append all new lines after the loop
  APPEND LINES OF lt_new TO lt_table.
  
  
  Use a different loop method or logic that does not require modifying the table during iteration.
  
  
  If you must modify the table during iteration, consider using a WHILE loop with an index and carefully manage the index to avoid conflicts.
  
  
  
  Related Information:
  
  This warning is a safeguard to prevent runtime errors or unpredictable behavior.
  The message class is usually W8 (Warnings related to internal tables).
  Similar issues can occur with other table modifications like INSERT, DELETE, or MODIFY during iteration.
  Always separate reading and modifying operations on internal tables.
  
  
  Summary:
  
  
  
  Aspect
  Description
  
  
  
  
  Cause
  Attempting to APPEND to an internal table while reading or looping over the same table.
  
  
  Effect
  SAP raises warning W8130 to prevent inconsistent table state.
  
  
  Solution
  Collect new entries separately and append after the loop, or restructure the code logic.
  
  
  Related
  Avoid modifying internal tables during READ or LOOP operations to maintain data integrity.
  
  
  
  
  If you want, I can help you refactor your specific code snippet to avoid this warning. Just share the relevant code!