private void dropTable(String[] tabs) throws Exception {
    conf.setBoolVar(HiveConf.ConfVars.HIVE_SUPPORT_CONCURRENCY, false);
    for (String tab : tabs) {
      driver.run("drop table if exists " + tab);
    }
    conf.setBoolVar(HiveConf.ConfVars.HIVE_SUPPORT_CONCURRENCY, true);
  }
txns update same resource but do not overlap in time - no conflict.
ql/src/test/org/apache/hadoop/hive/ql/lockmgr/TestDbTxnManager2.java