ok, briefly can you say (default tomcat6 installation) the server.xml has to do anything with database connection pools, any tag with param? default tomcat6 installation is ready bu default for this...?
Tomcat is built up out of components. The server.xml file describes how those components will be built up, configured, and connected together. The Thread Pool is just one of those components. People can - and frequently do - add components that provide database connection pool facilities in server.xml, although it's also common to define connection pools on a per-application Context level.
Some people, when well-known sources tell them that fire will burn them, don't put their hands in the fire.
Some people, being skeptical, will put their hands in the fire, get burned, and learn not to put their hands in the fire.
And some people, believing that they know better than well-known sources, will claim it's a lie, put their hands in the fire, and continue to scream it's a lie even as their hands burn down to charred stumps.