You can enable MMap to change its default parameters. You can also enable MMap for a particular context if the server is running in single-process mode. To do so, edit the sun-web.xml file for the web application as in the following example. Note that persistence-type must be set to mmap.
<sun-web-app> ... <session-config> <session-manager persistence-type=”mmap”> ... </session-manager> ... </session-config> ... </sun-web-app>
For more information about the sun-web.xml file, see Chapter 9, Deploying Web Applications.