If you are already familiar with DBMT, you might be aware of this;  if you are new to DBMT, you can save some time reading this article

DBMT is a new feature in Domino 9.0 that allows you to configure the regular maintenance options that you are familiar with to run automatically on schedule to keep your databases running smoothly. There are a lot of options that are described in the Administration Help Database

But, the Administration Help is wrong in one particular case:

“Specify any additional system databases using the notes.ini variable DBMT_FILTER. Separate entries in the list either by a space ( ), a comma (,) or a semi-colon (;). The names are case-insensitive and are relative to the data directory. ”

The correct name for the variable is DBMT_COMPACT_FILTER

Even after upgrading to 9.0.1, you will find this incorrect entry in the help.