Message type: E = Error
Message class:  DAAG_DESIGNTIME - Message Class for Data Aging Design Time 
Message number: 321
Message text: Number of key fields for table &1 set to maximum possible number
You have left the <LS>Number of Used Key Fields</> field empty or
entered the value  '<LB>0</>'. Neither of these entries are permitted.
The system has changed the value. All of the &V2& key fields (maximum
number) of table &V1& are used.
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.
The SAP error message DAAG_DESIGNTIME321 indicates that the number of key fields for a database table has reached the maximum limit allowed by the SAP system. This limit is typically set to 16 key fields for a table in the ABAP Dictionary.
Cause: The error occurs when you attempt to define or modify a database table in such a way that the number of key fields exceeds the maximum limit. This can happen during the creation of a new table or when trying to add additional key fields to an existing table.
Solution: To resolve this error, you can consider the following approaches: Review Key Fields: Check the existing key fields of the table and determine if all of them are necessary. If some key fields are not essential for the table's functionality, consider removing them. Composite Keys: If you have multiple fields that are being used as keys, consider whether you can combine some of
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