I had found it a while ago from another post on here:
Try this receipe:
The current System ID is 987654-32-0. Say you want to change this to 987654-32-1.
First halt the VSIM and enter into the bootloader prompt. Set the new serial ID there as shown.
SIMLOADER> set SYS_SERIAL_NUM="987654-32-1" SIMLOADER> boot
On booting if the system complains that it can't find it's disks then that's because software disk ownership is doing the right thing and keeping the disks allocated to the older system (old serial number). If so, ctrl-c into maintenance mode and re-assign the disks to the new ID.
I hope this response has been helpful to you.
At your service,
NetAppU Instructor and Independent Consultant (P.S. I appreciate points for helpful or correct answers.)
Do you mean you want to change the IDs in DFM DB? I would suggest that its better to change the IDs & Serial nos. as outlined in reply marked correct answer Eugene Kashpureff in this thread so that it gets added to your DFM DB as two different DOTs rather than other way round.
For sims to be unique in DFM DB they need to be of different SystemID as well as Serial No. You can set them while the sims are booted first time after unzipping from download.