Offline database is very interesting subject, and there are a couple of interesting details associated with it, which one must know.
There are two common queries related to offline database:
1)     My hard drive is getting full and I deleted my ‘offline’ databases. After deleting my offline databases, my hard drive is still full and there is no empty space.
2)     I recently deleted the ‘offline’ database, and now, when I am attempting to create database with the same name, it is giving me error that the database file already exists.
I can see why these questions are coming up frequently. The common understanding that seems to prevail is that when any database is deleted, files associated with the database (.mdf, .ndf and .ldf) are deleted automatically. This is true for any database that is an ‘online’ database. However, the behavior is bit different in the case of the ‘offline’ database. When any ‘offline’ database is deleted, files associated with the database are not deleted automatically. All the files related to the ‘offline’ database need to be deleted manually after deleting the offline database.
Reference: Pinal Dave (https://blog.sqlauthority.com)
