Message type: E = Error
Message class:  CNV_20100 - Messageclass for chart of account conversion 
Message number: 260
Message text: Impl. merge of sec. CostEl &1 with G/L acct &2 due to merge in exist. CoA
The system found that the secondary cost element &V1& is converted
into &V3& (according to the mapping). However there is already a
G/L account &V3&, which does not get converted into another value.
In effect, this means that a secondary cost element and a G/L account
are going to be merged (implicit merge). This is not allowed.
The conversion cannot take place.
The mapping table must be adjusted accordingly.
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 CNV_20100260 typically occurs during the data migration process, particularly when using the SAP S/4HANA Migration Cockpit or during the conversion of a system to S/4HANA. This error indicates that there is an issue with merging secondary cost elements with General Ledger (G/L) accounts due to a merge in the existing Chart of Accounts (CoA).
Cause: Chart of Accounts (CoA) Configuration: The error arises when there are conflicts in the mapping of secondary cost elements to G/L accounts during the migration process. This can happen if the same cost element is being mapped to multiple G/L accounts or if there are inconsistencies in the CoA setup. Data Migration Issues: If the data being migrated contains duplicates or conflicts in the definitions of cost elements and G/L accounts, this error can occur. Inconsistent Master Data: The master data for cost elements and G/L accounts may not be aligned, leading to issues during
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