Ontape with disk

Hi, All! I heard that ontape can manage with hard disk as good as with tapes. But how should it be organized? Simple change TAPEDEV/LTAPEDEV to the file doesn't work, I've got messages like - could not write log tape Of course file has the right perms. Perhaps it will possible organize some pipes... I just don't know. I guess it should be FAQ, but I didn't find out any help there, and in Usenet archive too. Thank you, -- Alexander Dron, IDS