FreeTDS Development Group

[Michael Peppler <mpeppler AT peppler.org>]

On Feb 22, 2012, at 11:32 PM, Michelle Dupuis wrote:

> I have a C program using freetds ver 0.91 (package on CentOS 5.7).  All 
> seems to work well, but after some idle time (eg: 5 hours) the connection 
> seems to drop because attempts to issue a query result in error 20003 
> (disconnect).  Is freetds disconnecting or is the Sybase server 
> disconnecting the session?
> Is there any way to prevent this?

Normally, Sybase will not disconnect an idle session. However, there are ways 
to enable this (e.g. checking on various MDA tables, and killing idle 
connections), so you check with your DBA that this is not in place on the 
database side.
I'm not 100% up to date on the FreeTDS internals, but I don't think that it 
has any idle disconnect logic (I know for a fact that Sybase OpenClient does 
not).
Another possibility is that there is a router or firewall between your 
program and the Sybase server, and it does idle disconnect - this is 
something that is fairly common - so maybe check with your network admins.

If I remember correctly I think that Sybase OpenClient has an option to turn 
on a keep-alive probe - I don't know if FreeTDS has included anything 
similar. Enabling this should at least fool the network layer into thinking 
that there is activity and avoid any disconnects from routers/firewalls.

Michael
--
Michael Peppler
Sybase on Linux FAQ: http://www.peppler.org/FAQ/linux.html

"A successful [software] tool is one that was used to do something undreamed 
of by its author." -- S. C. Johnson