Installed Tomcat 9.0.89 on ubuntu, with openjdk 11.0.22.. without altering anything, starting up Tomcat I see

/usr/lib/jvm/java-... -Xms512M -Xmx1024M -server ... 

Where does those -Xms/x come from? I cannot find any thing about that in the *.sh files in Tomcats bin folder. Created an setenv.sh file, thought I could overwrite the default values with

export CATALINA_OPTS="$CATALINA_OPTS -Xmx2048M"

but that only gives me two -Xmx in the start commando. I’d like to understand where the “initial” comes from..