I have Windows server running Apache Tomcat 8 and GeoServer 2.17. The JDK installed when setup is older, JDK 1.8.0_73.
I've now installed JDK 1.8.0_251. I changed my global env variable JAVA_HOME=C:\Progra~1\Java\jdk1.8.0_251\jre from JAVA_HOME=C:\Progra~1\Java\jdk1.8.0_73\jre
I cannot find anywhere a conf or XML or other file under the Tomcat folder that would specifically point to a particular Java version. I assumed then that environment variable Java_Home would be followed.
I've restarted Tomcat, then rebooted the machine entirely. When Tomcat starts, I go to GeoServer's Status page, and it clearly states that the JVM in use is still the _073 version.
Any hints as to where I would find that Tomcat is configured to use a particular JVM?