I had a discussion with @rsudev on irc last friday. 

So now, if isDbOnSdCard, I will do the following:
* delete the maybe copied db file from the target folder
* close db at the source folder
* move the closed db file from source to target folder
* init db file at target folder

So after this change, there is the same behaviour like in dbOnSdCard setting.

I will be at irc now to discuss while I'm doing the change.