private void updateLogLevel(final LogConfig logConfig,
      final LogLevelUpdateScope logLevelUpdateScope) {
    Level level = toLevel(LogWriterLevel.find(logConfig.getLogLevel()));

    Configuration configuration =
        getRootLoggerContext().getConfiguration();

    Collection<LoggerConfig> loggerConfigs = new HashSet<>();

    for (LoggerConfig loggerConfig : configuration.getLoggers().values()) {
      switch (logLevelUpdateScope) {
        case ALL_LOGGERS:
          loggerConfigs.add(loggerConfig);
          break;
        case GEODE_AND_SECURITY_LOGGERS:
          if (loggerConfig.getName().startsWith(GEODE_LOGGER_PREFIX)) {
            loggerConfigs.add(loggerConfig);
          }
          break;
        case GEODE_AND_APPLICATION_LOGGERS:
          if (!loggerConfig.getName().equals(SECURITY_LOGGER_NAME)) {
            loggerConfigs.add(loggerConfig);
          }
          break;
        case GEODE_LOGGERS:
          if (loggerConfig.getName().startsWith(GEODE_LOGGER_PREFIX) &&
              !loggerConfig.getName().equals(SECURITY_LOGGER_NAME)) {
            loggerConfigs.add(loggerConfig);
          }
      }
    }

    updateLogLevel(level, loggerConfigs.toArray(new LoggerConfig[0]));
  }
Name of variable that is set to "true" in log4j2.xml to indicate that it is the default geode
config xml.
geode-log4j/src/main/java/org/apache/geode/logging/log4j/internal/impl/Log4jLoggingProvider.java