How can I prevent data from being overwritten?

Whether we update or append a record is determined by whether or not a record with the same primary key exists in the target table. If such a record exists, we update. If not, we append. The default primary key for a Salesforce record, for example, is the id column. You can override the default primary key by specifying any combination of columns in data source definition.

Another option is to enable history tables. The Panoply team can turn on history tables for you. All we need is a list of the tables for which you would like history enabled. Keep in mind that turning these on will use more disk space than is currently consumed. Send your request via Help > Contact support within the Panoply platform, or contact us here in the Community.