Problem with add Database source

Hi I started with BI server 3.8.0 stable. When I want to add a new source database, I put the values and connect correctly to my DB2 source, after that I define the SQL command correctly too(I see the preview ok), but later I press the Finish button the system gives me an error: an error as encountered while saving the model file. check your server logs for details. Why appears this error? I have to configure anythings else? Where are he server log? Please help to fix this, thanks