I need a best practice, how to upgrade Implementer2008 to implementer 12.0. Thanks
Perhaps one of the Implementer support folks may come across your post, but I'd suggest opening a Support case with Implementer support, as I imagine the upgrade path from 2008 to 12.0 has a few considerations.
In the interim, some of it is covered in the Implementer Install admin guide,
Although that is a pretty big version jump, the installer should handle it just fine.
Make sure you have a reliable backup (always best practice when upgrading anything) and do the upgrade.
Personally, I would suggest you do a test upgrade beforehand just to make sure there aren't any problems.