The migration process only copies data from the local Cassandra to the remote Cassandra cluster, and while the migration is ongoing the new data is written to both the old local db and the new clustered one, so if the migration process was aborted halfway, the data loss in the local Cassandra database should be minimal.

I believe nothing needs to be done after aborting the migration tool, as the db config only gets changed after the migration was finished.

You can always make a copy of the C:\Skyline DataMiner\db.xml file, so you can restore the config to point your DMA to the old local Cassandra if this was already changed and you want to go back to using the old db.

https://docs.dataminer.services/user-guide/Reference/Skyline_DataMiner_Folder/More_information_on_certain_files_and_folders/DB_xml.html?q=db.xml