code: public void logMerge(String parity, String source, String codecId, 
        int[] checksums, long timestamp) {
      MergeOp op = MergeOp.getInstance();
      op.set(parity, source, codecId, checksums, timestamp);
      logEdit(op);
    }
docs: Merge(parity, source, ...) log
  It's used for converting old raided files into new format
  by merging parity file and source file together into one file