@Override
  public void acquireReadLock() {
    // not needed. The only thread
    // using this method is the async recovery thread.
    // If this placeholder is replaced with a real region,
    // this is done under a different lock

  }
This constructor is used when we are closing an existing region. We want to remember that it is
still present in the disk store.
geode-core/src/main/java/org/apache/geode/internal/cache/PlaceHolderDiskRegion.java