I was trying to find out the difference between Apache Tomcat variables - CATALINA_OPTS and JAVA_OPTS in SO and surprised to see that there is no question/answer posted here yet. So I thought of sharing it here (with answer) after finding out the difference. Check the answer/difference below.
NOTE: At the time of this posting, we're running Apache Tomcat v6.0.10 with JDK 6u32 on CentOS5 64-bit arch.
There are two environment variables - CATALINA_OPTS and JAVA_OPTS - which are both used in the catalina.sh startup and shutdown script for Tomcat.
CATALINA_OPTS: Comment inside catalina.sh:
# CATALINA_OPTS (Optional) Java runtime options used when the "start",
# "run" or "debug" command is executed.
# Include here and not in JAVA_OPTS all options, that should
# only be used by Tomcat itself, not by the stop process,
# the version command etc.
# Examples are heap size, GC logging, JMX ports etc.
JAVA_OPTS: Comment inside catalina.sh:
# JAVA_OPTS (Optional) Java runtime options used when any command
# is executed.
# Include here and not in CATALINA_OPTS all options, that
# should be used by Tomcat and also by the stop process,
# the version command etc.
# Most options should go into CATALINA_OPTS.
So why are there two different variables? And what's the difference?
Firstly, anything specified in EITHER variable is passed, identically, to the command that starts up Tomcat - the start or run command - but only values set in JAVA_OPTS are passed to the stop command. That probably doesn't make any difference to how Tomcat runs in practice as it only effects the END of a run, not the start.
The second difference is more subtle. Other applications may also use JAVA_OPTS, but only Tomcat will use CATALINA_OPTS. So if you're setting environment variables for use only by Tomcat, you'll be best advised to use CATALINA_OPTS, whereas if you're setting environment variables to be used by other java applications as well, such as by JBoss, you should put your settings in JAVA_OPTS.