How To Fix DU621 - Key blocks may have an extension in one direction only

DU621 - Overview

• Message type: E = Error

• Message class: DU - Data transfer to SAP-EIS

• Message number: 621

• Message text: Key blocks may have an extension in one direction only

Self-Explanatory Message

Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.

To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.

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DU621 - Details

• The SAP error message DU621, which states "Key blocks may have an extension in one direction only," typically occurs in the context of data modeling or database design within SAP systems, particularly when dealing with hierarchical data structures or key blocks in data definitions.
  
  Cause:
  This error usually arises when there is an attempt to extend a key block in both directions (i.e., both upwards and downwards) in a way that violates the constraints of the data model. In SAP, key blocks are used to define the structure of data records, and they must adhere to specific rules regarding their extensions. The error indicates that the current configuration or definition of the key blocks is not valid according to these rules.
  
  Solution:
  To resolve the DU621 error, you can take the following steps:
  
  
  Review Key Block Definitions: Check the definitions of the key blocks involved. Ensure that they are defined correctly and that any extensions