help with database and devices

I have a problem I need to deatach 2 devices from the tempdb and beable to use them in a new db im going to create , How can I do this I tried (alter database tempdb log off mydev='10M') I get the following error, ------ you cannot shrink database 'tempdb' because the database either has reduced durability or is being used as a template---. Anyone else have a solution to my problem? please helpp. I'm using ASE 15.7