Apparently you are attempting to publish multiple webapps under the context name of /ConnectionPooling. Each deployed webapp in
Tomcat must have a unique context name, since that's how the URLs get routed to specific webapps. So you need to find and remove the duplicates from wherever they are.
For what you're doing you
really shouldn't be modifying server.xml at all. For several years now, that's been discouraged, since it has significant disadvantages. It's better to make context XML files in $TOMCAT_HOME/conf/Catalina/localhost. DON'T attempt to define a context in both server.xml and conf/catalina/localhost, since Tomcat treats them as though they were all one big file, and that will give you a "duplicate context name" error.
If you're using that infernal useless Eclipse WST web plugin, it WILL muck with server.xml, but you shouldn't. Neither should they, technically, but they insist that they want to be compatible with Tomcat 3, even though even Tomcat 4 went end-of-life years ago.
Also,
JDBC drivers should be placed in the Tomcat lib directory and NOT in the WAR. If you put a driver jar in both places, you may end up with classpath problems.