In the log file of the firebird, a second before stopping all users, have this line:

SRVHYPERV2 Tue Jul 16 08:40:11 2013
Database: D:\WORK\DATA.FDB
deadlock
internal Firebird consistency check (Can't lock alloc table for reading)

Thereafter, the system uses the database stopped on all machines and process nBackup just stood, had to terminate the processes, start the firebird and merge the delta file.

Sorry again about my english.

--- In firebird-support@yahoogroups.com, "Leyne, Sean" <Sean@...> wrote:
>
> Matthias,
>
> > We have Firebird 2.5.2.26540, using SuperClassic, 70 users, our
> > database file has 2GB, we schedule nbackup every 20 minutes to make a
> > incremental backup, after implantation we had a problem, on average once a
> > day and happens deadlock and the firebird service stops and we have to "kill"
> > on the task manager to start again. If I disable NBackup not happen deadlock.
>
> Please explain your meaning of "deadlock".
>
> Nbackup can significantly consume available disk IO resources while it is running. Please provide details on the disk subsystem which you are running on.
>
>
> Sean
>