If you are not using Data Mining, Shared Services, custom defined functions, triggers, or external authentication, you can reduce the amount of memory used by editing essbase.cfg and setting JvmModuleLocation to null (empty).
If you are using these features, and need to reduce the amount of memory used, then you can reduce the JVM heap size by setting the following environment variables:
ESS_JVM_OPTION1=-Xmx16m
Because the default minimum and maximum for JVM heap size are different for different platforms and versions, set the correct value for your environment. For example, see the following as a reference: http://publib.boulder.ibm.com/infocenter/wasinfo/v4r0/index.jsp?topic=/com.ibm.support.was.doc/html/Java_SDK/1132680.html.