You might be able to do it WITHOUT touching your app.db (i.e the lazy way)
FW3.60 ONLY (At least on FW3.6 if it breaks you can fix it again)
1. Before you start make a backup of your app.db (just in case) i normally just use vitashell to copy it somewhere safe on the memory card
2. With VITASHELL make a new directory in ux0:/PSPEMU/PSP/ - i ccall mine BACKUP
3. Use VITASHELL to browse to the folder of the bubble you wanna clone (PSPEMU/PSP/GAME/[GAMEID] - where [GAMEID] is your PSP game to clone)
4. Copy that folder to your backup folder
5. Rename the ORIGINAL folder by adding a number 2 on the end e.g DISCID2
6. Copy the folder back from your backup folder to game folder.
7. EITHER - use recovery menu to rebuild database OR easyinstaller by freakler to rebuild database - CAUTION this wipes layout etc and whitelist mods etc, I never have any installed (Did i mention im lazy)
8. check out your bubbles. Ensure both boot - if its the ePSP bubble dont forget to run henkakau first though.