[Zope] Zope 2.7.3 database pack fails

Well, the ol' Data.fs got bigger (now 3.9GB) and so it's time to cut it back down to size. Unfortunately, just clicking "pack" on the control panel does not seem to do the job. This Data.fs has a history (2.5.1b3, 2.6, and now 2.7.3). The question is, how to pack it.