Google Gears - Database - VACUUM

With this code:

var db = google.gears.factory.create('beta.database');
db.open('cominar');
db.execute('CREATE TABLE IF NOT EXISTS Ajax (AJAX_ID INTEGER PRIMARY KEY AUTOINCREMENT , MODULE TEXT, FUNCTION TEXT, CONTENT_JSON TEXT);');
db.execute('VACUUM;'); // nettoye la DB

      

        
        
        
      

    

I am trying to clear the database (VACUUM) on every initialization, but I get this error:

Fault Error: Database operation failed. ERROR: permission denied DETAILS: not authorized

The database was created by me (on the same page).

Thanks!