In Teiid Designer after you first create your models you can run the preview feature to query a table, but once you close JBDS and re-open it the Preview no longer works on your existing tables. Gives the popup error "Error running preview see log for more details" click OK then another popup error "Validate the username and password in the default Teiid Server" ( this error is a red herring though, the username and password are correct) Looking in the server.log you'll see the error that the corresponding Preview.vdb doesn't exist. It doesn't exist because once you close JBDS this is deleted from the deploy directory, but it should be re-created every time you open JBDS and run the Preview and isn't.