As a last resource, I installed the same old software in the new
server, so I had

Penium IV 3.0 GHz, 1 GByte RAM
Fedora Core 2, Linux kernel 2.6.5-1.358
FirebirdSS-1.5.2.4731-0

To my surprise, after half a day running with no problem, the firebird
server didn't respond any more ( using interactive isql, and trying to
CONNECT to any database, it times out after one minute or two ) with
the following error:

SQL> connect /opt/databases/webhammer.fdb ;
Statement failed, SQLCODE = -902

Unable to complete network request to host "localhost".
-Failed to establish a connection.

I got no lock manager out of room message, neither did I find a
database I/O error message in the firebird.log, as I found before.

The only thing I found in the firebird.log was

servin.argencasas.com (Client) Tue Feb 27 23:11:47 2007
/opt/firebird/bin/fbguard: guardian starting bin/fbserver

servin.argencasas.com (Server) Wed Feb 28 14:36:26 2007
INET/inet_error: select in packet_receive errno = 9

servin.argencasas.com (Server) Wed Feb 28 14:36:26 2007
SCH_validate -- not entered

The timestamp of the last error is the same as the timestamp of the
database file, so it is logical to assume that that was the last time
the database was updated, and from that point on, the server stopped
responding.

More, the last error (SCH_validate) is the same observed when debian
was installed, before the database file access errors and, probably,
before the lock manager out of room.

Needless to say, as "service firebird stop" command didn't work, I had
to shut down firebird with the following commands :

killall fbguard
killall fbserver

So, debian distribution, kernel version and firebird releases has
nothing to do with this stuff.

My first question, in order to begin undertand error messages, is what
is "SCH_validate -- not entered" error ?

Aldo