I would suggest closing the data tables immediately after they are not needed with Close(datatablereference, No Save), but it will require most likely a bit more scripting to add those to correct locations.
So here is a script to which should close all datatables starting with subset:
Names Default To Here(1);
tableList = Get Data Table List();
for(i = 1, i <= N Items(tableList), i++,
currentTableName = tableList[i] << Get Name;
isSubsetTable = Starts With(Lowercase(currentTableName), "subset");
If(isSubsetTable,
Try(
Close(tableList[i], no save);
Print("Closed data table: " || currentTableName ||"."),
show(exception_msg));
);
);
-Jarmo