  We derive astrophysical and structural parameters of open clusters NGC 1245
and NGC 2099 from 2MASS JHKs and Gaia DR2 photometric / astrometric data bases.
Their likely members have been determined from Gaia DR2 proper motion data. Our
E(B-V) values (2MASS) are slightly smaller than the literature values, whereas
our E(B-V) values (Gaia DR2) agree with the literature within the
uncertainties. Their distance moduli/distances and ages are in good coincident
with the literature. NGC 1245 has steep negative core mass function slope (MFs)
({\chi}_core=-1.24). Its halo ({\chi}_halo=+0.78) and overall
({\chi}_overall=-0.95) MFs mean that it presents signs of small-scale mass
segregation to the outer regions from its core, due to its [{\tau}_rlx
(overall),{\tau}_overall ]=[302 Myr,5]. The MFs of NGC 2099 is very negative
steep ({\chi}_core=-2.67) in the core, and quite positive steep
({\chi}_halo=+1.41) in the halo. This kind of MF slope steeping from the core
to the outskirts indicates that low-mass stars in the core are transferred to
the cluster's outskirts, while massive stars sink in the core, because of mass
segregation. NGC 2099's flat overall MFs ({\chi}_overall=+0.91) and its
{\tau}_overall=8 presents a sign of mass segregation. These OCs with the
relatively large masses 8700 Msolar (NGC 1245) and 5660 Msolar (NGC 2099),
which locate at RGC > 9 kpc, expose to external perturbations such as tidal
effects and shock waves, and they lose their stars in low-proportions.
