m.Th.,

> Forgive my ignorance, but then what about is this entire thread
> talking about? What is the SERVER-A.LCK file from our server and
> how/from where fb_lock_print collects the data which throws in the
> screen?

In many cases the operating system implements shared memory between
distinct process through the memory mapping of files. Whilst this
link between files and shared memory isn't necessary, it has proven
convenient over the past 20, 30 years.

You may want to read about BSD's mmap (now also in posix):
http://www.die.net/doc/linux/man/man2/mmap.2.html
, about SYS V IPC:
http://users.actcom.co.il/~choo/lupg/tutorials/multi-process/multi-
process.html
and about the Win way of doing things, which presumably is based on
the VMS way:
http://www.byte.com/art/9410/sec14/art3.htm

If you are really interested in this, you may want to deep dive into
some unix system programming books before digging into the Firebird
source.

Paul