Catalog retention duration impacts the size of DPM database. The longer the duration, the bigger the database size will be. ...

Catalog retention duration impacts the size of DPM database. The longer the
duration, the bigger the database size will be.

The database size also depends on other factors, such as number of jobs and
number of protected members. The database size cannot be reduced using DPM.
Reducing the size of the tape catalog may ensure that the DPM database does 
not continue to grow.