title: How to get total unused pages from firebird nbackup
body: <p>I'm using firebird nbackup method to backup my database by using this code:</p>
  
  <p><code>nbackup -u systemdab -p masterskeys -B 0 DB01.FDB DB01.NBK</code></p>
  
  <p>After complete backup, the size is smaller than original size. It might be caused of removing unused pages (I'm new to firebird please correct me if I'm wrong). </p>
  
  <p>Is there any possible way to prevent removing of unused pages, or any way to get the amount of unused pages inside my database ? </p>
  
  <p>Please let me know if you have any idea. Thanks.</p>