What is a connection pool?
Connection pool handles the connections to a database requested from a particular web server process. It caches the database connections, so that connections can be reused thus improving the performance.
If you are running out of connections you will get the following server error:
"Host connection pool not found"
How to increase the number of connections in connection pool?
In "installation folder" \tomcat\conf\Catalina\localhost\ROOT.xml file set the maxActive attribute to the prefered value.