Hi Olaf,

> Database "D:\INTERBASE\IFLS.GDB"
>
> Database header page information:
>
> Flags 0
>
> Generation 2939162
>
> System Change Number 0
>
> Page size 4096

You might consider increasing to 8K, especially when the tree depth of an index starts to become > 3. To be checked with gstat -i.

> ODS version 12.0

Indeed, the database was created with Firebird 3. ;-)

> Oldest transaction 2893677

The "oldest interesting" transaction (OIT) in a state other than committed, e.g. also rolled back. There are no record versions for transactions < 2893677 available (cause they have been garbage collected), thus one could say why the marker is called "interesting".

> Oldest active 2929833

The oldest transaction currently active/running. This is the lowest transaction ID which should be visible in MON$TRANSACTIONS.

> Oldest snapshot 2878316

This is the oldest transaction started in snapshot mode. Hope I remembered that correctly.

> Next transaction 2938824

Transaction id for the next new transaction.

> Sequence number 0
>
> Next attachment ID 87910
>
> Implementation HW=Intel/i386 little-endian OS=Windows
> CC=MSVC
>
> Shadow count 0
>
> Page buffers 0

The default value in firebird.conf is used for the size of the page cache of the database. Might be too small, depending on your use case.

> Next header page 0
>
> Database dialect 3
>
> Creation date Mar 7, 2016 18:33:37
>
> Attributes force write
>
>
>
> Variable header data:
>
> Sweep interval: 5000

That's not a good idea. Because if the difference of OIT and OST (oldest snapshot) reaches that threshold, a sweep will kick in, visits all records in the database and removes out-dated record versions which are not interesting for other transactions anymore.

Regarding OIT/OAT movement/gaps etc., commit retaining is one of your #1 enemies. Usually used behind the scene by drivers with auto commit = ON.

--
With regards,
Thomas Steinmaurer
http://www.upscene.com

Professional Tools and Services for Firebird
FB TraceManager, IB LogManager, Database Health Check, Tuning etc.

>
> *END*
>
>
>
>
>
>
>
> Von: firebird-support@yahoogroups.com
> [mailto:firebird-support@yahoogroups.com]
> Gesendet: Donnerstag, 14. April 2016 14:03
> An: firebird-support@yahoogroups.com
> Betreff: Re: [firebird-support] How to interprete gstat-results
>
>
>
>
>
>> Hello @ll,
>>
>>
>>
>> we are using firebird 3.0 RC2 and have some questions about open
>> transactions. (Clients connect over odbc) The gstat output gives 70000
>> transactions between the oldest and the current transaction, if we look
> into
>> the monitoring table, we see only 10 transactions. The "oldest one" we
>> cannot find in this table. What is the oldest transaction and which roll
>> does the garbage collector play? If we have many open transactions, the
>> performance is bad. What role plays the attachments? What is the best way
> to
>> check the performance bottleneck in such cases?
>
> Please post an entire gstat -h output.
>
> --
> With regards,
> Thomas Steinmaurer
> <http://www.upscene.com> http://www.upscene.com
>
> Professional Tools and Services for Firebird
> FB TraceManager, IB LogManager, Database Health Check, Tuning etc.
>
>
>
>