In most cases we recomend using the mod_proxy /apache combination as a frontend to tomcat. However for those looking to squeeze extra performance out of a bare tomcat installation the following may be useful
Apache Portable Runtime (APR) and Tomcat
Per http://apr.apache.org/ Tomcat can use the Apache Portable Runtime to provide superior scalability, performance, and better integration with native server technologies.
Installing the JNI wrappers for APR used by Tomcat (libtcnative)
Throughout the documentation, there are references to the two following properties:
CATALINA_HOME: Represents the root of your Tomcat installation, for example /home/tomcat/apache-tomcat-9.0.10 or C:\Program Files\apache-tomcat-9.0.10.
CATALINA_BASE: Represents the root of a runtime configuration of a specific Tomcat instance. If you want to have multiple Tomcat instances on one machine, use the CATALINA_BASE property.
If you set the properties to different locations, the CATALINA_HOME location contains static sources, such as .jar files, or binary files. The CATALINA_BASE location contains configuration files, log files, deployed applications, and other runtime requirements.