private void ensureVlfCapacity() {
    int vlfOffsetsCapacity = 0;
    if (vlfOffsets != null) {
      vlfOffsetsCapacity = vlfOffsets.length;
    }
    if (vlfCount == vlfOffsetsCapacity) {
      int[] tmp = new int[vlfOffsetsCapacity + EXPAND_SIZE];
      for (int i = 0; i < vlfOffsetsCapacity; i++) {
        tmp[i] = vlfOffsets[i];
      }
      vlfOffsets = tmp;
    }
  }
Make sure we have room to add a VLF offset.
geode-core/src/main/java/org/apache/geode/pdx/internal/PdxWriterImpl.java