private ConfigurationPersistenceService checkForClusterConfiguration()
      throws PreconditionException {
    ConfigurationPersistenceService result = getConfigurationPersistenceService();
    if (result == null) {
      throw new PreconditionException("Cluster Configuration must be enabled.");
    }
    return result;
  }
Returns true if any connections exist
geode-connectors/src/main/java/org/apache/geode/connectors/jdbc/internal/cli/ListMappingCommand.java