look at the Field.xml file in the raw ASDM directory. There should be many fields listed.
OR: if you've already created the ms, look in the listobs file. If you have less than ~6 fields, chances are you have a problem.
OR: run au.plotmosaic(,sourceid=. If not a mosaic (usually just 1 circle drawn), there is a problem.
Workaround is described in http://jira.alma.cl/browse/CSV-2999 (see comment from Eric Villard on 30/Nov/13). You will need scriptForCSV2999.pywhich is attached to that ticket.
See Adam's note in CSV2999: In any dataset with Tsys issues to be fixed via au.repairSysCal , the Tsys needs to be fixed BEFORE applying your fix here. Otherwise repairSysCal gets confused mapping fields and names.