"Data export started. It may take some time based on the amount of data. For more details, check the log files. Invalid objects found in the input command: nr Failed to execute the Database Export process. For more details, check the log at NX_ROOT/log/dbpromote.log. SLUMP died!!! Aborting the process."
Release : 17.1
Component : SERVICE DESK MANAGER
This is a known error and has been reviewed under Defect id - DE42929 and updated that "this is only a error message, but no impact on the functionality".
So this message can be ignored and proceed ahead with db_promote.
Go to Administration tab -> System -> Data Export From here you can import/export as well. Also can verify the history even if performed from command line under Data Export/Import History List.