FreeTDS Development Group

["James K. Lowden" <jklowden AT freetds.org>]

On Tue, 1 May 2012 11:33:34 +1000
"box.eugene" <box.eugene AT gmail.com> wrote:
> I am new to freetds and have some questions about intermittent error
> below that we get from our monitoring system that uses freetds for
> SQLServer connect check:
> 
> ALERT                  : Unable to connect to instance
> ERROR TEXT             : OpenClient message: LAYER = (0) ORIGIN = (0)
> SEVERITY = (78) NUMBER = (35)
> Server <server_name_here>, database Message String: SQL Server
> connection timed out.

At my last place of employ we had a long-running SQL Server watchdog
process that would fail intermittently.  I was never able to determine
if the problem was in FreeTDS, the network, the server, Windows, or
cygwin.  On a couple of occasions when I quickly checked the server, I
was momentarily unable to connect to SQL Server using the machine's own
keyboard.  But the situation resolved itself within a minute or two.  

> 1) What does "LAYER = (0) ORIGIN = (0) SEVERITY = (78) NUMBER = (35)"
> error mean

They are CT-Library terms, and not particularly meaningful.  FreeTDS's
implementation of the ct-lib error message propagation is
rough-and-ready. 

> what can be the cause of this error?

If you are encountering behavior similar to what I described, I suspect
either a bug in SQL Server or a disagreement at the TCP layer between
Windows and Linux on what the protocol does.   

> 2) I am not sure if it is genuine connect issues (some intermittent
> network problems) or freetds bug/wrong configuration/high load (we
> check hundreds of databases each run)

It's not a configuration problem.  With enough patience and resources,
we could definitely track it down.  So far, the problem is small enough
that no one has bothered.  

HTH.  

--jkl