tx.begin();
OQLQuery query = odmg.newOQLQuery();
query.create("select aLotOfArticles from " + Article.class.getName() + " where productGroupId = 4");
DCollection results = (DCollection) query.execute();
results = results.query("price > 35");
// now perform control query
query = odmg.newOQLQuery();
query.create(
"select aLotOfArticles from "