If your application code is handling a second Database, there shuld be no problem with this;
but keep in mind this:
you cannot have more than 100 active targets in your app, i.e. if you use 2 Device Databases and you want to activate them simultaneously, the total number of targets may not exceed the 100 units anyway.
For example, 2 Databases of 50 targets each will be OK (50 + 50 = 100), as well as 1 Database with 80 targets + a second DB with 20 (80 + 20 = 100);
but it will not be possiblefor instance to simultaneusly activate 2 DB with 100 targets each (total would be 100 + 100 = 200, i.e. greater than 100, not allowed).
So, to summarize, you can load several databases at the same time, but only activate them simultaneously if their total target count is within the 100 limit.
If this limit is exceeded, you will have to activate one of them only, and if you activate one, you will have to deactivate the other, and vice versa.