FreeTDS Development Group

[Alberto Pulvirenti <alberto.pulvirenti AT crowdengineering.com>]

Hi,

maybe I forgot to clarify a point. The failure I mention refers to the
function dbcmd().
I checked with a personal MS SQL Server I use for testing and I saw that
when the connection is faulty or the DB server is down, what happens is
that either the dbsqlsend() fails (and then I catch it) or the dbsqlok()
stays pending for a long time.
Whenever I try to switch off the server, it stops always there, never at
the dbcmd() level.

In all the documentations I see, when dbcmd fails it is always explained as
a memory problem, and it happens before one tries to send to the server
itself. That's what confused me.

It is surely possible that in a moment a memory occupancy spike took place
which caused this momentary failure (because, maybe I didn't stress this
point, but this failure was not a persistent condition, it happened just
once or twice and then the communication succeeded).

Thanks for any advice.

Alberto

2012/12/4 Frediano Ziglio <freddy77 AT gmail.com>

> 2012/12/4 Alberto Pulvirenti <alberto.pulvirenti AT crowdengineering.com>:
> > Dear all,
> >
> > unfortunately, searching on google seemed to be unsuccessful for this,
> and
> > I didn't find any help looking ad previous discussions (maybe since I
> > subscribed this mailing list).
> >
> > I have manage to set up a connection to a MS SQL database server using
> > freeTDS, but it sometimes (seldom, fortunately) happens that a dbcmd
> fails.
> > Looking at the various documentations, it should be a problem of memory
> > allocation, but this happened even for extremely simple queries like a
> > "begin transaction", and not always for the same query: it just happened
> in
> > a given moment, and it was not either possible to reproduce this problem,
> > but I remained afraid that it can appear again.
> > I don't really understand how can dbcmd fail with such a simple query
> when
> > the machine is not stuck (which I would think if it is a problem is so
> > serious that even such a small string cannot be allocated).
> >
> > The MS SQL server stays in another machine to which I must connect
> through
> > network, although it is a machine internal to the location where all this
> > stuff runs. Can it happen that a sudden and momentary communication
> failure
> > causes dbcmd() to fail? Or its failure are only due to memory allocation
> > problems?
> >
> > Is there any way I can adopt to deeper check this problem?
> >
> > Thanks
> >
> > Alberto
>
> Personally I would exclude a memory problem. If the system fails to
> allocate few bytes of memory you should note other problems (unless
> you set some limits on your program for instance using PHP module
> which limit memory itself).
>
> It's possible that connection got broken for some reason (a simple
> service restart or a backup schedule which put database in some
> particular state). Or even that server disconnect you cause you where
> idle for too time (see recent keepalive discussion).
>
> Frediano
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