  Coded caching schemes are used to reduce computer network traffics in peak
time. To determine the efficiency of the schemes, \cite{MN} defined the
information rate of the schemes and gave a construction of optimal coded
caching schemes. However, their construction needs to split the data into a
large number of packets which may cause constraints in real applications. Many
researchers then constructed new coded caching schemes to reduce the number of
packets but that increased the information rate. We define an optimization of
coded caching schemes under the limitation of the number of packets which may
be used to verify the efficiency of these schemes. We also give some
constructions for several infinite classes of optimal coded caching schemes
under the new definition.
