Seems to be /etc/default/tomcat56
Edit your file with SUDO GEDIT /etc/default/tomcat6
Check your current JAVA_OPTS and you can add lines like this at the end:
<span class="Apple-style-span">JAVA_OPTS</span>
<span class="Apple-style-span">="${JAVA_OPTS} -Xms1024m -Xmx1024m"
</span>
### ONLY ONE THAT WORKS!!!
