DIRMC makes it , for example,
possible to keep directories in dedicated primary disk pool.
Provided there are no new bugs related to DIRMC
this brings significant speed gain during restore of directory trees.

So, unless you are backing large files / large amount of files / in small
number of directories, do alter existing configuration.

Make a simple test: point-in-time restore blah blah -dirsonly,
once from tape pool and once from disk pool, you will understand.

regards
juraj Salak