FreeTDS Development Group

["James K. Lowden" <james.k.lowden AT icloud.com>]

On Thu, 14 Apr 2016 09:18:34 +0200
<jezekj AT centrum.cz> wrote:

> We have tried tracing on several levels and we have found that in
> FreeTDS trace log messages are written at every itteration. However
> in UnixODBC trace messages are shown when procedure finishes.
>
> [...] Is freeTDS bufferring messages on it's output (but after
> tracing log is written), or are these messages buffered in the
> UnixODBC?

If you look at the FreeTDS logging function, you'll see it opens and
closes the logfile each time a message is written.  That ensures each
message is flushed to the disk, but it's very expensive in terms of
performance.  You don't want to use TDSDUMP in production.  

>From your description, it sounds like you're using log message to
monitor your application's data status.  If so, I would counsel you
that that's a mistake.  Better at the application level to capture the
statistics you need and flush them under application control (or, you
know, insert them in a table).  Then you don't have to worry about the
vagaries of ODBC log buffering.  

HTH.

--jkl