There are purchased items on the iPad Error message

I am having the issue with my iPad. After I updated iPad to 3.2.1, I was greeted with the same message, as if I should download some apps with iTunes."There are purchased items on the iPad "iPad" that have not been transferred to your iTunes library. You should transfer these items to your iTunes library before updating this iPad. Are you sure you want to continue?"Then I had to do the transfer.