tds/src/main/java/thredds/featurecollection/InvDatasetFcFmrc.java
protected void update(CollectionUpdateType force) throws IOException {  // this may be called from a background thread, or from checkState() request thread
    logger.debug("update {} force={}", name, force);
    boolean changed;
    MFileCollectionManager dcm;
    switch (force) {
      case always:
      case test:
        dcm = (MFileCollectionManager) getDatasetCollectionManager();
        changed = dcm.scan(false);
        if (changed)
          super.update(force);
        break;

      case never:
        return;

      default:
        super.update(force);
    }
  }
protected void update(CollectionUpdateType force) throws IOException {  // this may be called from a background thread, or from checkState() request thread
    logger.debug("update {} force={}", name, force);
    boolean changed;
    MFileCollectionManager dcm;
    switch (force) {
      case always:
      case test:
        dcm = (MFileCollectionManager) getDatasetCollectionManager();
        changed = dcm.scan(false);
        if (changed)
          super.update(force);
        break;

      case never:
        return;

      default:
        super.update(force);
    }
  }
/* @Override  // overriding superclass -WHY?
public void update(CollectionUpdateType force) {
fmrc.update();       // so when is work done?
}