The parameter ds.tomcat.maxmemory (set as a -D option in the tomcat section of Monitor.xml) is used along with ds.tomcat.memcheck to determine memory usage thresholds in the tomcat JVM at which DocuShare will perform its 'memory management' actions.
Memory Management is performed when free memory falls below a given percentage of so-called 'max memory'. Max Memory is computed by taking the value of the option ds.tomcat.memcheck and multiplying it by 1M, or by taking the value of the default configured memory of the JVM if ds.tomcat.memcheck is not set (e.g., Runtime.totalMemory() ).
The value of percentage is taken by using the value of the option ds.tomcat.memcheck or using 10 (e.g., 10%) if the value is not set.
If neither the value of ds.tomcat.memcheck or ds.tomcat.maxmemory is set, then Memory Management is off and not performed.
If Memory Management is on, then if memory falls below "ds.tomcat.memcheck" percent of "ds.tomcat.maxmemory", computed as described above, then garbage collection is run at every request where memory falls in the computed range, and cached HTTPSession data is discarded. This data is used for things like saving lists of collections or users or groups used by choosers, and other purposes. DocuShare may well run slower when memory reaches this level.
To see what your site is running at for these settings, look at tomcat.stdOut for a logging line like this (output at INFO logging level)
Max memory=, free memory when less than which is % of max memory