  The non-Markovianity of the stochastic process called the quantum semi-Markov
(QSM) process is studied using a recently proposed quantification of memory
based on the deviation from semigroup evolution, that provides a unified
description of divisible and indivisible channels. This is shown to bring out
the property of QSM processes to exhibit memory effects even in the
CP-divisible regime, in agreement with an earlier result. An operational
meaning to the non-Markovian nature of semi-Markov processes is also provided.
