Wow. The "Ozone Layer" has a surface now. Cool. But let me answer your question:
Because ozone is created as a result of UV striking O2 in the upper troposphere, we only find "holes" at the north and south polar regions, during their respective winters. In order to reduce the size of those cyclical, seasonal thinnings, we'll need to create a second sun that shines on the opposite pole of whichever side the current sun is shining on currently.
That would end the seasonal cycles, and Life on Earth, but you wanted those pesky holes reduced. I'm sure it will be a fair trade, in the end.