The following example describes the effect on process size when configuring the persistence-type="mmap" using the manager-properties properties (documented for the MMapSessionManager in the Sun Java System Web Server 6.1 Programmer’s Guide to Web Applications):
maxSessions = 1000 maxValuesPerSession = 10 maxValueSize = 4096
This example would create a memory mapped file of size 1000 X 10 X 4096 bytes, or ~40 MB. As this is a memory mapped file, the process size will increase by 40 MB upon startup. The larger the values you set for these parameters, the greater will be the increase in process size.