  We report an analysis of photometric behaviour of DI UMa, an extremely active
dwarf nova. The observational campaign (completed in 2007) covers five
superoutbursts and four normal outbursts. We examined principal parameters of
the system to understand peculiarities of DI UMa, and other active cataclysmic
variables. Based on precise photometric measurements, temporal light curve
behaviour, O-C analysis, and power spectrum analysis, we investigated physical
parameters of the system. We found that the period of the supercycle now equals
31.45 +/-0.3 days. Observations during superoutbursts infer that the period of
superhumps equals P_sh = 0.055318(11) days (79.66 +/- 0.02 min). During
quiescence, the light curve reveals a modulation of period P_orb = 0.054579(6)
days (78.59 +/- 0.01 min), which we interpret as the orbital period of the
binary system. The values obtained allowed us to determine a fractional period
excess of 1.35% +/- 0.02%, which is surprisingly small compared to the usual
value for dwarf novae (2%-5%). A detailed O-C analysis was performed for two
superoutbursts with the most comprehensive coverage. In both cases, we detected
an increase in the superhump period with a mean rate of dot_P/P_sh =
4.4(1.0)*10^{-5}. Based on these measurements, we confirm that DI UMa is
probably a period bouncer, an old system that reached its period minimum a long
time ago, has a secondary that became a degenerate brown dwarf, the entire
system evolving now toward longer periods. DI UMa is an extremely interesting
object because we know only one more active ER UMa star with similar
characteristics (IX Dra).
