but your config file doesn't point to that. It points to realmd_bc and to mangos_bc which are not part of the "YA" database. They are separate.
I don't think you can have them as a nested database, which is how they seem to be configured right now. I wouldn't even know how to begin to configure mangos to recognize that the two databases were under another DB. They need to be in the first tier as two separate databases.
In other words you can't just rename YA to anything.
Just click on the realmd_bc db that is right above the ya database and edit those settings in that DB. That is the one Mangos is connecting to.