title: What do I need to do to DataMapper to have a persistent sqlite database?
body: <p>Here's what I'm using to create my database:</p>
  
  <pre><code>DataMapper.setup(:default,"sqlite://my.db")
  
     class Model1
  
        property :some_prop,String
        ...
        property :other_prop,String
     end
  
     DataMapper.auto_upgrade!
  </code></pre>
  
  <p>I'm using this in combination with Sinatra. Everything's ok while the script is running, I can use my objects normally. However, I see no file <code>my.db</code> on the disk, and everytime I'm restarting the application, I start from scratch, without any objects.</p>
  
  <p>What am I doing wrong?</p>