code: public boolean connect() throws OntopConnectionException {
          try {
              if (localConnection != null && !localConnection.isClosed()) {
                  return true;
              }
              if (settings.isPermanentDBConnectionEnabled()) {
                  localConnection = LocalJDBCConnectionUtils.createConnection(settings);
                  return localConnection != null;
              }
          } catch (SQLException e) {
              throw new OntopConnectionException(e);
          }
  
          return true;
      }
docs: Keeps a permanent connection to the DB (if enabled in the settings).
  
  Needed by some in-memory DBs (such as H2).