By default archivetar will hand off transfers to globus to manage and not wait for them to finish. This is ok in most cases but not ones where you want to know the transfer is complete before modifying / deleting data or scripting multiple archives.
The --wait option tells archivetar to wait for all Globus transfer to finish. It will also print print Globus performance information as it runs.
The option --rm-at-files implies --wait for tars only and not transfers created by the --size option.