void testHookCloseAllOverflowChannels() {
    synchronized (overflowMap) {
      for (OverflowOplog oo : overflowMap.values()) {
        FileChannel oplogFileChannel = oo.getFileChannel();
        try {
          oplogFileChannel.close();
        } catch (IOException ignore) {
        }
      }
    }
    synchronized (compactibleOverflowMap) {
      for (OverflowOplog oo : compactibleOverflowMap.values()) {
        FileChannel oplogFileChannel = oo.getFileChannel();
        try {
          oplogFileChannel.close();
        } catch (IOException ignore) {
        }
      }
    }
  }
@param minSize the minimum size this oplog can be
geode-core/src/main/java/org/apache/geode/internal/cache/OverflowOplogSet.java