@Override
  public byte[] getValueArray() {
    throw new UnsupportedOperationException(
      "Tag is backed by an off heap buffer. Use getValueByteBuffer()");
  }
This is a {@link Tag} implementation in which value is backed by {@link java.nio.ByteBuffer}
hbase-common/src/main/java/org/apache/hadoop/hbase/ByteBufferTag.java