Thank you Helen,
you pointed me to the right direction.
I calculated the bytes in my SQL statement and they are 76,705 bytes, more
than the accepted range of the 65,535 bytes.
Reducing the SQL query length, solved the problem.
Is there any way to disable the firebird behavior of disconnecting users
when it things that it is under attack? In my case, the firebird server is
located in a local intranet without any danger from the outside.
Yianni
2010/2/3 Helen Borrie <[email protected]>
> At 11:54 AM 3/02/2010, you wrote:
> >I am trying to execute a long Update sql statement but I am getting an
> Dynamic SQL Error (error code -104).
>
> That code is virtually useless, since it encompasses *all* DSQL errors.
> You need to capture the 9-digit ISC error code.
>
> >After that error I loose the connection with the database for some strange
> reason.
>
> If you have a string overflow in the connection string, then the reason is
> not strange at all. Firebird will block any string overflow attempts that
> it detects in a connection request, since this is the most common way that
> bad guys have to instigate a denial-of-service attack on your server.
>
> >Steps to reproduce:
> >
> >1. Download the solution from this link:
> ><http://www.grbytes.com/downloads/Firebird_sql_error.rar>
> http://www.grbytes.com/downloads/Firebird_sql_error.rar
> >
> >2. Run the project and click on the "Create Connection" button to create a
> connection with the database
> >
> >3. Click the "Execute SQL" button to execute the long update statement.
> You will see the error. Please notice that the connection with the database
> is also lost for some reason. If you click again the "Execute SQL" button
> you will see an other error.
> >
> >It looks like a bug, but I am not sure.
> >My question is if there is a limitation for the length of the sql
> statement
>
> Yes, it is 65,535 bytes. That comprises every byte that is passed in the
> statement, including the value of all the parameters, white spaces, quote
> characters, etc. Note, BYTES, not characters.
>
> >and why the connection is lost after failing to execute it?
>
> The connection will be lost if the server thinks it is in danger of a DoS
> attack. However, that's only one (fairly unusual) example of what can break
> a connection. Applications should be checking what they pass across the
> interface, BEFORE they submit requests.
>
> If you are getting the same problem every time with this statement, and not
> otherwise, that tends to finger either that statement, either its content or
> the manner in which it is being submitted. The first clue will be that ISC
> code. Even if your application is not smart enough to pick it up, it will
> appear in firebird.log, chronologically near some network error reports, if
> the server process managed to survive the episode long enough.
>
> Bear in mind, too, that if your "long update statement" means "lots of
> records updated in one transaction", then maybe your batch size is too large
> for the amount of machine resources available to the server. Around 8000
> records per transaction has long been regarded as a base "maximum" batch
> size to work backwards or forwards from to arrive at an optimal batch size
> for the resources available.
>
> Also, if your update is repeatedly updating the *same* records all within
> the same transaction, that is NOT recommended practice. It has a high
> chance of causing something to burst.
>
> Helen
>
>
>
>
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