Message type: E = Error
Message class:  CNV_LTHCM_S_10 - LT HCM: Message Class for Data Selection 
Message number: 026
Message text: Specify way of selecting relationships
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The SAP error message CNV_LTHCM_S_10026 with the description "Specify way of selecting relationships" typically occurs in the context of data migration or conversion processes, particularly when using the SAP Landscape Transformation (SLT) or SAP Data Services tools. This error indicates that the system requires a specific method or criteria for selecting relationships between data entities, but this has not been defined.
Cause: Missing Selection Criteria: The error usually arises when the user has not specified how to select relationships in the data migration or transformation process.
Configuration Issues: There may be a misconfiguration in the settings related to the data migration project. Incomplete Data Mapping: The relationships between source and target data entities may not be fully defined or mapped.
Solution: To resolve this error, you can take the following steps: Define Selection Criteria: Go to the relevant configuration or mapping screen in your data migration tool. Specify the criteria for selecting relationships. This could involve defining filters, conditions,
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