{.global.} in global scope

[dawkot]

What does the global pragma do the way it is used 
[here](https://github.com/Araq/ormin/blob/master/examples/forum/forum.nim)? 
    
    
    import "../ormin/ormin", json
    
    importModel(DbBackend.sqlite, "forum_model")
    
    var db {.global.} = open("stuff", "", "", "")
    ...
    
    
    Run