I didn't post any code because i think this is a general problem: simple daemon that updates mysql db once per 10 sec using alarm signal.

That's like saying "I didn't post any code, because it's just a little CGI that does some stuff and prints HTML" ... the devil is in the details.

As a general rule: If you have a question about why some code doesn't do what you expect. Post the code (or the smallest sample program that demonstrates the problem).

In situations where your question concerns an err msg you are getting, the "general rule" becomes the golden rule: If you are getting an eror, from code you think should work, post a sample program that generates the error, and the exact text of the error, along with your question.