Bret,
Thank you for the response!
I am completely aware of the fact that SAP does not recommend moving tempdb off master because of potential recovery issues. However, the recovery procedure is well documented, for those who really want to go ahead with the procedure.
In any case, this exercize was completely academic in nature, and to show the use of segments, and the function of the sysdatabases, sysdevices and sysusages tables as well as how to set a database in single user mode, or for that matter to start the whole server in single user mode. Tricky on Windows.
In any case, will try your procedure. However, I thought there was another way that did not involve re-creating tempdb completely. In other words, can´t you "migrate" the first fragment of sysusages off master and to the new device?
As far as playing with system tables, well, I used to do it all the time, for well defined goals when I did support at JPMChase. BTW, if you start the server in single user mode, you don´t need to put ANY database in "single user" or ¨dbo use only" modes.
Regards,
Jean-Pierre