How do I change the working directory for tomcat?

by default, this directory is $JBOSS_HOME/server/my_conf/work.

The work directory is a configuration option on the host in $JBOSS_HOME/server/your_conf/deploy/jbossweb-tomcatxx.sar/server.xml

you can enter e.g.

<Host name="localhost" autoDeploy="false" deployOnStartup="false" deployXML="false" workDir="/my/work/dir">