When we putting more than 3 applications in Tomcat Webapp, we might experience slowness and eventually application crash, even after we have increase Tomcat reserved memory. It is normally refer as Out of Memory Error in PermGen space.
Default PermGen space size is 64MB. To increase it, similar to increase Tomcat reserved memory, we need to edit $TOMCAT/bin/catalina.bat (or catalina.sh in Linux) and look for JAVA_OPTS:
set JAVA_OPTS = ""
-XX:PermSize=500m -XX:MaxPermSize=500m to JAVA_OPTS. If JAVA_OPTS exists with other parameters, just append the new parameters to it.
set JAVA_OPTS = "-Xms2000m -Xmx2000m -XX:PermSize=500m -XX:MaxPermSize=500m"
It is recommended to set size as 1/4 of the reserved memory, eg 1/4 of the 2GB reserved memory will be 500MB PermGen space size.
Other reference: 2 solution of java.lang.OutOfMemoryError in Java