Hoi Jan,
backup operation opens a snapshot transaction and this will cause
transaction inventory/header modifications, GC etc..
So, your DB be not in application use but, using by backup tool.
You can set readonly mode it with gfix if you don't want any
modification/change.

Regards.
Ali

--- In firebird-support@yahoogroups.com, Jan Bakuwel
<jan.bakuwel@...> wrote:

>
> Hoi all,
>
> Not a very urgent question at all but one that has kept me

curious :-)

>
> Please see below a list of backups of a Firebird 1.5.1 database

that is

> currently not in use (the db has moved to another machine). The
> automatic backup procedure was still running...
>
> How is it possible that the resulting outputfile of gbak is

different in

> size? Intended behaviour?
>
> cheers,
> Jan