I've done this in two steps: 3.1.2.x to 3.7.x and then to 4.1.  I believe we
tested the jump from 3.1.2.x to 4.1 directly and had some problems but I
haven't been able to prove that and I haven't tested it myself.

There is a directory path change but the installation procedure will
probably fix that up for you.  I know it did on Solaris.

Standard drill: ensure you have all the information necessary for a disaster
recovery: db backup, know where it is, devconfig file, volhist file, etc.
Plan, Plan, Plan.  When I did this on a Solaris box (only to 3.7) I planned
for two hours and upgrade took 20 minutes.  I think if I had planned for 20
minutes I'd still be working on the upgrade!

Thanks,

Kelly J. Lipp
Storage Solutions Specialists, Inc.
PO Box 51313
Colorado Springs CO 80949-1313
(719) 531-5926
Fax: (240) 539-7175
Email: lipp AT storsol DOT com or lipp AT storserver DOT com
www.storsol.com
www.storserver.com