  We present in this paper a self-reproducing comparator P~system that
simulates insertion sort. The comparator $\Pi_c$ is a degree-2 membrane and
structured as $\mu = [_{h_0} [_{h_1}]_{h_1} [_{h_2}]_{h_2} ]_{h_0}$. A
maximizing $\Pi_c$ compares two multisets $a$ and $b$ where $\min(|a|,|b|)$ is
stored in compartment $h_1$ while $\max(|a|,|b|)$ is stored in compartment
$h_2$. A conditional reproduction rule triggers $\Pi_c$ to clone itself out via
compartment division followed by endocytosis of the cloned compartment. We
present the process of sorting as a collection of transactions implemented in
hierarchical levels where each level has different concurrent or serialized
steps.
