Database design: one database or multiple databases, which is best?
We have a database which has about a 100 or so tables, accessed by about five different applications. Five different applications have their own set of tables but also need to access about 20 master tables (used by all our systems: users, accounts, contacts, shops, etc). Now we are going to have another 15 or so applications with their own set of tables but also again need access to get information from the master tables. So before we get set up what do you think is the best schema and database set up. i.e. one database with all applications including the master ones. Each application has its own database with the master records staying in master?
Anyone's thoughts here would be much appreciated. I think I am leaning towards separate databases so they can be managed better, and performance should be better (maybe not?).
If I go with separate are their any implications: setting up references wont be possible, performance joining databases for selects, updates, asp.net needs 2 connections strings (is that even possible with say entity framework database first or LINQ DBML).