Subject Re: [firebird-support] Firebird SuperClassic hangs
Author Alexey Kovyazin
Hi Freddy,

Try to use optimized Firebird configuration

As Sean already told, hang could be caused by very long processing of some requests - extremely long queues in lock table, or related with excessive number of record versions (Max Versions in database statistics), or with other reasons.  I would recommend to perform detailed investigation of the problem.

Alexey Kovyazin




we’re running Firebird 2.5.7 SuperClassic on Windows Server 2012R2 as part of a web application. Database is around 130GB with millions of transaction per day. From time to time Firebird hangs. It does not respond to any client. It’s also not possible to connect locally to the server. The interesting thing is the memory consumption that drops from 5-7GB to around 50MB and the CPU load goes down to 0%. When Firebird is in this state, I also see a lot of waiting threads in the Task Manager under “Analyze wait chain”. The only way to get out, is to stop the service. This takes longer than normal and sometimes shows some kind of timeout. But the process is stopped and can be started again. I also ran  fb_lock_print when the problem occurred. It shows something under “Deadlock scans” which is not normal, I think.



                Version: 145, Active owner:      0, Length: 25165824, Used: 24798216

                Flags: 0x0001

                Enqs: 17157097538, Converts: 22693011, Rejects: 12135777, Blocks: 93039760

                Deadlock scans:    289, Deadlocks:      1, Scan interval:  10

                Acquires: 18346589405, Acquire blocks: 1203176111, Spin count:   0

                Mutex wait: 6.6%

                Hash slots: 1009, Hash lengths (min/avg/max):   47/  67/  93

                Remove node:      0, Insert queue:      0, Insert prior:      0

                Owners (151):   forward:  30704, backward: 21097392

                Free owners (4):             forward: 750216, backward: 24346456

                Free locks (10120):         forward:  28728, backward: 693760

                Free requests (7877):    forward: 8570432, backward: 1678000

                Lock Ordering: Enabled


Has anybody experienced something like this? Thanks in advance.


Best regards

Freddy Ertl