Subject AW: [firebird-support] Question about transactions
Author Olaf Kluge
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Olaf Kluge

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-----Ursprüngliche Nachricht-----
[] Im Auftrag von Helen Borrie
Gesendet: Mittwoch, 3. Dezember 2008 14:08
Betreff: Re: [firebird-support] Question about transactions

At 09:00 PM 3/12/2008, you wrote:

>ive a problem with out database.

I don't think you have a problem with your database....yet.

>The size of the file increase and increase. Here are the status:
>flags: 0
>checksum: 12345
>generation: 3311
>page size: 4096
>ods version: 11.1
>oldest transaction: 86
>oldest active: 87
>oldest snapshot: 87
>next transaction: 3303
>bumped transaction: 1
>sequence number: 0
>next attachement ID: 9
>implementation ID: 16
>shadow count: 0
>page puffers: 0
>next header page: 0
>database dialect: 3
>creation date: dec. 3, 2008, 10: 30:42
>attributes: force write
>variable header data:
>sweep interval: 20000
>The firebird.log containt the follow messages:
>DBSRV (Server) Wed Dec 03 10:24:46 2008
> INET/inet_error: read errno = 10054

That is just a network message..but it pre-dates the creation date of your
database, anyway.

>Im using firebird 2.1 superserver
>Some Clients has a connection to firebird (java netbeans). One Procedure
>does update one table 10 times in a second (state-table) Is this a problem?


>Please, can you help me, how can I make the database more stable? How can
>the database protect itself?

What instability do you observe? You have not described any.

>This problem I have on more firebird database (upper size in a few days)

A new (or newly restored) database will grow quickly until its size becomes
"big enough" to accommodate both your committed data and the garbage that
you keep there. When the DB engine needs more space for new records, or to
write new versions of existing records, it will try to find enough space on
existing pages. If it cannot find enough free space, it will ask the
operating system for more pages. Each time it gets a new page your database
file grows by 4 KB.

The database will settle into a steady growth pattern, once it has enough
pages and free space to keep pace with the actual increase of data and your
pattern of garbage collection. Of course, if you are writing applications
that inhibit garbage collection, the database has no choice other than to
keep growing. Space occupied by "interesting" garbage remains trapped and
unavailable for re-use.

"Interesting" garbage is garbage from an older transaction that is still
interesting to one or more newer transactions. It remains interesting until
those newer transactions are committed.

We can see from your header statistics that you are building up a stack of
active transactions, perhaps 2-3000 in an hour; but that is not a problem,
since this is a very new database and these statistics were probably
reported while several users were busy.

Keep an eye on the changes in the statistics: if the gap between the Oldest
Active and the Oldest Snapshot does not change much over a long period, or
if the gap between the Oldest and the Oldest Snapshot is going into many
thousands, then you probably do have a garbage problem. The suggested
monitoring tools would help to find the offending uncommitted transactions
and could indicate places in your application code, where insufficient care
is being take to commit work in a prompt and timely way.




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