  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 and thus providing a unified
description of divisible and indivisible channels. This is shown to bring out
the property of QSM process to exhibit memory effects in the CP-divisible
regime. An operational meaning to the non-Markovian nature of semi-Markov
processes is also provided.
