Message type: E = Error
Message class:  CNV20551 - message for package 20551 (company code delete) 
Message number: 318
Message text: Pool &1 : Pool table &2 is cross-client and will NOT be deleted
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The SAP error message CNV20551318 indicates that there is an attempt to delete a cross-client pool table, which is not allowed in SAP. Cross-client tables are shared across all clients in an SAP system, and their data is not specific to any single client. Therefore, SAP restricts the deletion of such tables to maintain data integrity and consistency across clients.
Cause: The error occurs when: A data migration or conversion process attempts to delete entries from a cross-client pool table. The table in question is defined as a cross-client table in the SAP data dictionary (DDIC).
Solution: To resolve this error, consider the following steps: Review the Process: Check the data migration or conversion process that is attempting to delete the entries. Ensure that it is not trying to delete data from a cross-client table. Modify the Logic: If the deletion is necessary, you may need to modify the logic to exclude cross-client tables from the deletion process.
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