  We revisit hydrogen shell burning on white dwarfs (WDs) with higher mass
accretion rates than the stability limit, \dot M_stable, above which hydrogen
burning is stable. Novae occur with mass accretion rates below the limit. For
an accretion rate > \dot M_stable, a first hydrogen shell flash occurs followed
by steady nuclear burning, so the shell burning will not be quenched as long as
the WD continuously accretes matter. On the basis of this picture, some
persistent supersoft X-ray sources can be explained by binary models with high
accretion rates. In some recent studies, however, the claim has been made that
no steady hydrogen shell burning exists even for accretion rates > \dot M_{\rm
stable}. We demonstrate that, in such cases, repetitive flashes occurred
because mass accretion was artificially controlled. If we stop mass accretion
during the outburst, no new nuclear fuel is supplied, so the shell burning will
eventually stop. If we resume mass accretion after some time, the next outburst
eventually occurs. In this way, we can design the duration of outburst and
interpulse time with manipulated mass accretion. We call such a controlled nova
a "forced nova." These forced novae, if they exist, could have much shorter
recurrence periods than "natural novae." We have obtained the shortest
recurrence periods for forced novae for various WD masses. Based on the
results, we revisit WD masses of some recurrent novae including T Pyx.
