Hi, all

I have a production system runs with firebird about 3 years. About week
ago the system's behaviour becamed very strange. Server almost stops
responding after N-th user have connected to the database. Suddenly
simple queries becames too heavy - execution time raises from
milliseconds to minutes. When it happens CPU load is extreme high on
first hardware and moderate on second (hardware configurations are
described below), system memory is not exhausted and HDD activity is low.

I've tried to check the database, backup/restore, upgrade Firebird from
1.5.0 to 1.5.1, switch from super to classic and back, migration to
another hardware - nothing helps. A few days ago server works before
hang about 3-4 hours. Now it takes a few minutes.

The system serves about 15-25 connections. The database size is about
350-400Mb, last year added about 100Mb.

Hardware: AMD Athlon XP3200+, 1.5Gb RAM, DPT Ultra-80 SCSI RAID 0 (3 x
9.1Gb HDD) + one standalone SCSI HDD for system boot, gigabit ethernet
controller, OS - Red Hat Linux 9.0 . I've tried another computer: Dual
Xeon 2.8 GHz, 2Gb RAM, 18Gb U160 SCSI HDD (10000RPM), gigabit ethernet
controller, OS - Fedora Core 1.

I suspect the following:
- the production database and security.fdb are descendants from beta
versions of Firebird 1.5 or even release 1.0 . But backup/restore of it
was not helped and ODS version is 10.1 now.
- My old, but simple UDFs stops working, but how they did work about 3
last years? And there are no server crashes. By the way it worked on the
same system at least from 1.5.0 release date (April or May)
- some fundamental OS limits have been reached.

And now the strangest thing: I've just replaced the HDD in the dual Xeon
system and installed the Firebird under W2003 Server there (affinity
mask was set to 15 in firebird.conf). The system is working excellent
under load already 4 hours.

Please help me to diagnose and solve the problem.

Andrew