The best answer is to use Integration Hub ETL (a free plugin). IH-ETL will guarantee that your data source is transformed via Robust Transform Entries and use the Identification and Reconciliation Engine (IRE) to properly identify your sources. (This does assume you are importing to CI classes that have identifier entries, so that statement doesn't hold for Business Applications, for example, as they don't have any identifiers.) There is a bit of a learning curve for IH-ETL but it is by far the best and most flexible and reliable option for you to import CIs into the CMDB. I would not recommend taking on the task of trying to use Robust Transform Engine directly, and there is no need to do so.
The opinions expressed here are the opinions of the author, and are not endorsed by ServiceNow or any other employer, company, or entity.
