So, how long do I have to give it, for 400GB of audio? I’ve been waiting for 4 hours already. While it is creating stems for the files in the background, nothing seems to happen with databases. Has this even been tested while it’s creating stems? Seriously, denon, this is just buggy as hell!
Optimize database at the same time as ongoing jobs? Of course it takes time then.
A lot of this depends on your computer’s capabilites and how you’re storing music. It’s not about how much audio, but rather the number of records in the DB, etc..
1.5tb +90k (mixed MP3, FLAC, ALAC & WAV) 5-6min without doing any other tasks or using other aplications.
Yeah, it does this stems creation in the background. You may want to WARN a user if it can’t do it at the same time. Seriously. Have they ever done some real-world testing with their code? Most current day software has zero issues multitasking. If it cannot optimize databases while other tasks are busy, that is just lazy coding. You can stop or lock the database service, then run the optimization, then start it again. Duh. This is what normal developers do.
How is that logical? Please explain. Every other software I have on my PC shuts down or pauses a database service (access) when it is optimizing dabases. It should do that by default, because if it would not do that, the db will get corrupted. Duh.
The question remains open: How long until it’s done, or I Ctrl-Alt-Del End-task EngineDJ ?
If you kill the task, you may run the risk of corrupting one or more databases if a binary file is open. 
I speak from experience 
Does Task Manager show any activity? It should not take hours and hours for even a 50GB Sqlite3 db.