Most people have been in a situation requiring them to change one or more of the parameters passed to the JVM on top of which JBoss AS is running. For instance - you may need a bigger heap, bigger perm gen size or something else. The best place to put these parameters is probably the following file:
where $JBOSS_HOME refers to the directory in which you’ve unpacked the JBoss AS distribution.
Look for this section:
if [ "x$JAVA_OPTS" = "x" ]; then JAVA_OPTS="..." fi
All you have to do now is adapt it to your needs.