Message type: E = Error
Message class:  CNV_PE - General messages for posting engine 
Message number: 178
Message text: Parameter &1 is a structure; structure parameters are not allowed
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The SAP error message CNV_PE178 indicates that a parameter being used in a conversion or migration process is a structure, and structures cannot be used as parameters in the context where they are being referenced. This error typically arises during data migration or conversion activities, particularly when using the SAP Landscape Transformation (SLT) or other data migration tools.
Cause: Incorrect Parameter Type: The error occurs when a structure is passed as a parameter to a function or method that expects a simple data type (like a single value or a scalar type).
Configuration Issues: There may be a misconfiguration in the data migration settings or mapping definitions where a structure was incorrectly defined or referenced. Coding Errors: If custom code is involved in the migration process, there may be a coding error where a structure is being passed instead of its individual fields.
Solution: Check Parameter Definitions: Review the parameters being passed in the function or
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