Hi all,
I have my client use stand alone Management Server and two Security Gateway with version R80.40. This server version R80.40 was upgrade from R77.30 use CPUSE methode and running smoothly. 
Now my client wan to upgrade from R80.40 to R81.20. On the Management Server, I find  the current root partition did not eough space for upgrade via CPUSE metnode. 
I found that i need to erase the existing partition and re-format the Harddisk then install a new R81.20 even use Advanced or Migration and Upgrade methode.
I also facing with import database error during Migration and Upgrade simulation process.
On the erase partition and re-format harddisk simulation. I try to re-install R80.40, install the require HF_Bundle, reload users backup file. Rebuild an operational R80.40 server.  Then I use CPUSE to upgrade server to R81.40 with successfull without error.
I want to know the above task. Is it a possible way to upgrade the serever with elimiate error during the upgrade process ? Any missing and wrong direction on the above task?
Best Regard.