--- In firebird-support@yahoogroups.com, "darklord28099" wrote:

>
> Hello all,
>
> I have a question about the growth of files while using nbackup.
> The .nbks created by nbackup seem to grow strangely over the course of usage. For example, on an empty database of 12.4 mb, first nbackups are as follows:
> Level 0 - 12.4 mb.
> Level 1 - 72.1 kb.
> Level 2 - 72.1 kb.
>
> The next runs of level 1 and level 2 backups are usually 80.1 kb in size, but the maximum values reached for the first day are 176.1 kb for a level 1 and 104.1 kb for a level 2.
>
> The next day, a new level 0 backup is made. This new backup is 12.9 mb in size. The maximum size for a level 1 for this day is 352.2 kb and for a level 0 is 120.1 kb. The third day of runs has the database growing to 13.4 mb with a maximum level 1 of 248.2 kb and level 2 of 136.1 kb.
>
> These file size changes occur when there are no transactions performed on the database; the system is simply idling. Is this to be expected with nbackup? Again, there are no changes being performed on the database, so the fluctuations in file sizes is unexpected.

nbackup maintains RDB$BACKUP_HISTORY storing there records about every created backup. It starts and commits transactions which is necessary to run SQL statements (such as ALTER DATABASE BEGIN|END BACKUP, etc). So there *is* changes even in the "idle" database.

Regards,
Vlad