Subject Re: [firebird-support] nbackup / gbak interoperation
Author Dimitry Sibiryakov
> Restore the file using gbak, overwriting the original file

You can't overwrite original file as long as somebody is working with
it, including nbackup.

> I'm thinking this would be a way to reclaim lost space in an OLTP system's db file without kicking off the users

There is no such things as "lost space" in Firebird DB. Database
pages are reused.