  We perform global three-dimensional MHD simulations of unstratified accretion
disks in cataclysmic variables (CVs). By including mass inflow via an accretion
stream, we are able to evolve the disk to a steady state. We investigate the
relative importance of spiral shocks and the magnetorotational instability
(MRI) in driving angular momentum transport and how each depend on the geometry
and strength of seed magnetic field and the Mach number of the disk (where Mach
number is ratio of the azimuthal velocity and the sound speed of gas). We use a
locally isothermal equation of state and adopt temperature profiles that are
consistent with CV disk observations. Our results indicate that the relative
importance of spiral shocks and MRI in driving angular momentum transport is
controlled by the gas Mach number and the seed magnetic field strength. MRI and
spiral shocks provide comparable efficiency of angular momentum transport when
the disk Mach number is around 10 and the seed magnetic field has plasma
$\beta=400$ (where $\beta$ is ratio of gas pressure and magnetic pressure). The
MRI dominates whenever the seed field strength, or the disk Mach number, is
increased. Among all of our simulations, the effective viscosity parameter
$\alpha_{eff} \sim 0.016-0.1$ after MRI saturates and the disk reaches steady
state. Larger values of $\alpha_{eff}$ are favored when the seed magnetic field
has vertical components or the flow has stronger magnetization ($1/\beta$). Our
models all indicate that the role of MRI in driving angular momentum transport
thus mass accretion in CV disks is indispensable, especially in cool disks with
weak spiral shocks.
