Both Jira and Confluence run on the Tomcat, it is critical for a Jira and Confluence system administrator to understand how Tomcat works. And what those paramaters mean in the server.xml? How to monitor the JMX metric to decide whether the server is healthy or not.
I found a blog article on Data Dog website which I think is a must read for every Jira and Confluence system administrator.
And also of course the official Tomcat document: