The docs say this:

The number of hours to retain entries in log mining history table. When set to 0, log mining history is is disabled.

It's not clear really why a user should or should not set this to values other than 0. What's the benefit/implication of having a "log mining history"?

Slightly related: the option should probably be renamed, as it's not related to the database history really. So it shouldn't be in the "database.history" option namespace.