The process for exporting and importing data is as follows:
Consider importing all records in your system, even those that have been resolved. By including all records, you can access historical information about your projects and immediately generate useful management reports.
You can import one record type at a time, including the history and attachment information for that record type. If you have multiple record types, you must import them in an order that allows referencing. For example, if you have a defect record type that refers to a project record type, import the project record before you import the defect record.
If you have duplicate records, you must import them separately. See Importing duplicate records.