code: private void removeEventWait(String eventName) throws SQLException {
          String query = "delete from EVENT_WAIT_INSTANCE where EVENT_NAME=?";
          db.runUpdate(query, eventName);
          this.recordEventHistory(eventName, EventLog.SUBCAT_DEREGISTER,
                  "N/A", 0L, "Deregister all existing waiters");
      }
docs: remove existing waiters when a new waiter is registered for the same event
  @param eventName
  @throws SQLException