> I'm creating a big load of connections to Firebird and during a select
> statement I reached the memory limit for Firebird. The select failed
> with:
> ISC ERROR CODE:335544430
>
> ISC ERROR MESSAGE:
> unable to allocate memory from operating system
>
> The machine is a VM with 2GB ram and Firebird was using at the time
> around 400Mb. However there were 884 threads running in Firebird and
> Firebird just froze.

Firebird used 2GB of *virtual memory* which is a limit for 32-bit process.
400MB you seen is amount of *physical* memory.

> Firebird log shows the following error:
> SRVR_multi_thread: forcefully disconnecting a port
>
> The Firebird server is not crashed and the guardian, of course, has not
> restarted it.

Don't use guardian !!! It do nothing which OS can't do. And it prevents
drWatson from creating crash dump (on Windows fo course).

> Should the guardian have been notified somehow or should Firebird have
> crashed gracefully?

Why should it crash ? Lower amout of connection and it should work normally.

Regards,
Vlad