@Override
  protected String _getUnmodifiableMsg(String name) {
    return String.format(
        "The %s configuration attribute can not be modified while the system is running.",
        name);
  }
Constructs an internal system config given an existing one.

@param dc an existing system configuration.
geode-core/src/main/java/org/apache/geode/distributed/internal/DistributionConfigSnapshot.java