While a file is being imported you can click the <Abort Import> button to abort the import. You are prompted to confirm that you really want to abort the import, or you can resume the import.
In general, it is not recommended that you abort an import because all records imported up to the point of the abort will remain in the database. The records imported prior to an abort are not un-done. However, all records that were not imported, i.e. records from the point of the abort up to the end of the import file, are appended to an unprocessed file. All records that were not successfully processed by the import are appended to the unprocessed file, and this includes the records that were not processed due to an abort.
You can process the remaining records by importing the unprocessed file. See Log and Unprocessed Files.