private boolean createPartitionedIndex(Formatter f) throws IOException {
    long start = System.currentTimeMillis();

    // create partitions based on TimePartitionCollections object
    for (CollectionManager dcm : tpc.makePartitions()) {
      tp.addPartition(dcm);
    }

    List<TimePartition.Partition> bad = new ArrayList<TimePartition.Partition>();
    for (TimePartition.Partition dc : tp.getPartitions()) {
      try {
        dc.makeGribCollection(f); // ensure collection has been read successfully
        if (trace) f.format(" Open partition %s%n", dc.getDcm().getCollectionName());
      } catch (Throwable t) {
        logger.error(" Failed to open partition " + dc.getName(), t);
        f.format(" FAIL on partition %s (remove) %n", dc.getDcm().getCollectionName());
        bad.add(dc); // LOOK may be a file leak ?
      }
    }

    // remove ones that failed
    for (TimePartition.Partition p : bad) tp.removePartition(p);

    // choose the "canonical" partition, aka prototype
    int n = tp.getPartitions().size();
    if (n == 0) {
      logger.error(" Nothing in this partition = " + tp.getName());
      f.format(" FAIL Partition empty collection = %s%n", tp.getName());
      return false;
    }
    int idx = tpc.getProtoIndex(n);
    TimePartition.Partition canon = tp.getPartitions().get(idx);
    f.format(" Using canonical partition %s%n", canon.getDcm().getCollectionName());

    // check consistency across vert and ens coords
    if (!checkPartitions(canon, f)) {
      logger.error(
          " Partition check failed, index not written on {} message = {}",
          tp.getName(),
          f.toString());
      f.format(" FAIL Partition check collection = %s%n", tp.getName());
      return false;
    }

    // make the time coordinates, place results into canon
    createPartitionedTimeCoordinates(canon, f);

    // ready to write the index file
    writeIndex(canon, f);

    // close open gc's
    tp.cleanup();

    long took = System.currentTimeMillis() - start;
    f.format(" CreatePartitionedIndex took %d msecs%n", took);
    return true;
  }
  private void createIndex(
      File indexFile, List<Group> groups, ArrayList<String> filenames, Formatter f)
      throws IOException {
    Grib2Record first = null; // take global metadata from here

    if (indexFile.exists()) indexFile.delete(); // replace it
    f.format(" createIndex for %s%n", indexFile.getPath());

    RandomAccessFile raf = new RandomAccessFile(indexFile.getPath(), "rw");
    raf.order(RandomAccessFile.BIG_ENDIAN);
    try {
      //// header message
      raf.write(MAGIC_START.getBytes("UTF-8"));
      raf.writeInt(version);
      long lenPos = raf.getFilePointer();
      raf.writeLong(0); // save space to write the length of the record section
      long countBytes = 0;
      int countRecords = 0;
      for (Group g : groups) {
        g.fileSet = new HashSet<Integer>();
        for (Grib2Rectilyser.VariableBag vb : g.rect.getGribvars()) {
          if (first == null) first = vb.first;
          GribCollectionProto.VariableRecords vr = writeRecordsProto(vb, g.fileSet);
          byte[] b = vr.toByteArray();
          vb.pos = raf.getFilePointer();
          vb.length = b.length;
          raf.write(b);
          countBytes += b.length;
          countRecords += vb.recordMap.length;
        }
      }
      long bytesPerRecord = countBytes / ((countRecords == 0) ? 1 : countRecords);
      f.format(
          "  write RecordMaps: bytes = %d record = %d bytesPerRecord=%d%n",
          countBytes, countRecords, bytesPerRecord);

      if (first == null) {
        logger.error("GribCollection {}: has no files\n{}", gc.getName(), f.toString());
        throw new IllegalArgumentException("GribCollection " + gc.getName() + " has no files");
      }

      long pos = raf.getFilePointer();
      raf.seek(lenPos);
      raf.writeLong(countBytes);
      raf.seek(pos); // back to the output.

      GribCollectionProto.GribCollectionIndex.Builder indexBuilder =
          GribCollectionProto.GribCollectionIndex.newBuilder();
      indexBuilder.setName(gc.getName());

      for (String fn : filenames) indexBuilder.addFiles(fn);

      for (Group g : groups) indexBuilder.addGroups(writeGroupProto(g));

      /* int count = 0;
      for (DatasetCollectionManager dcm : collections) {
        indexBuilder.addParams(makeParamProto(new Parameter("spec" + count, dcm.())));
        count++;
      } */

      // what about just storing first ??
      Grib2SectionIdentification ids = first.getId();
      indexBuilder.setCenter(ids.getCenter_id());
      indexBuilder.setSubcenter(ids.getSubcenter_id());
      indexBuilder.setMaster(ids.getMaster_table_version());
      indexBuilder.setLocal(ids.getLocal_table_version());

      Grib2Pds pds = first.getPDS();
      indexBuilder.setGenProcessType(pds.getGenProcessType());
      indexBuilder.setGenProcessId(pds.getGenProcessId());
      indexBuilder.setBackProcessId(pds.getBackProcessId());

      GribCollectionProto.GribCollectionIndex index = indexBuilder.build();
      byte[] b = index.toByteArray();
      NcStream.writeVInt(raf, b.length); // message size
      raf.write(b); // message  - all in one gulp
      f.format("  write GribCollectionIndex= %d bytes%n", b.length);

    } finally {
      f.format("  file size =  %d bytes%n", raf.length());
      raf.close();
      if (raf != null) raf.close();
    }
  }