Message type: E = Error
Message class:  CNV_MBT_09_A - Message class for drop-solution 
Message number: 354
Message text: View & was already active.
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The SAP error message CNV_MBT_09_A354 typically indicates that a view you are trying to activate or work with in the context of a data migration or conversion process is already active. This error is often encountered during the execution of the SAP S/4HANA Migration Cockpit or other data migration tools.
Cause: The error occurs because the system detects that the view you are attempting to activate is already in an active state. This can happen due to: The view being activated previously in the same session or transaction. A system inconsistency where the activation status of the view is not correctly reflected in the system. Multiple attempts to activate the same view without proper checks.
Solution: To resolve this error, you can try the following steps: Check Activation Status: Verify if the view is indeed active. You can do this by checking the relevant transaction or using the Data Dictionary (SE11) to see the status of the view. Refresh the
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