This is an extraction of the doc:
MMapSessionManager (Unix Only)
This is a persistent memory map (mmap) file based session manager that works in both single process and multi-process mode.
The MaxProcs directive in the magnus.conf file determines whether the server is running in single process mode or multi-process mode. For more information, see the NSAPI Programmer's Guide for iPlanet Web Server.
MMapSessionManager takes the following parameters:
maxSessions - the maximum number of sessions maintained by the session manager at any given time. The session manager refuses to create any more new sessions if there are already maxSessions number of sessions present at that time. The default value is 1000.
maxValuesPerSession - the maximum number of values or objects a session can hold. The default value is 10.
maxValueSize - the maximum size of each value or object that can be stored in the session. The default value is 4096.
timeOut - the amount of time in seconds after a session is last accessed by the client before the session manager destroys it. Those sessions that haven't been accessed for at least timeOut seconds are destroyed by the reaper method. The default value is 1800 (30 minutes).
If session-timeout is specified in web.xml, it overrides this timeOut parameter value. For details, see "session-timeout."
reapInterval - the amount of time in seconds that the SessionReaper thread sleeps before calling the reaper method again. The default value is 600 (10 minutes).
maxLocks - the number of cross-process locks to use for synchronizing access to individual sessions across processes. The default value is 1. This default value is used if the value 0 is specified. This parameter is ignored in single-process mode.
You may want to enable MMapSessionManager to change its default parameters. You can also enable MMapSessionManager for a particular context if the server is running in single process mode. To enable iPlanet Web Server to use MMapSessionManager, do any of the following:
Use the Legacy Servlets>Configure Global Servlet Attributes page in the Server Manager interface.
In the Session Manager field specify:
You can also specify parameters for the session manager in the Session Manager Args field, for example:
Edit the file servlets.properties in the directory server_id/config. This will apply to the default virtual server only.
Add a line specifying a value for servlets.sessionmgr and a line specifying the parameters for the session manager:
Edit the file contexts.properties in the directory server_id/config. This will apply to the default virtual server only.
Add a line specifying a value for context.context_name.sessionmgr and a line specifying the parameters for the session manager:
You can change the global context or define a new context and assign specific servlets to it. For more information, see Chapter 8 "Legacy Servlet and JSP Configuration."
This session manager can only store objects that implement java.io.Serializable.
Deleting SessionData Version Files
If the server uses the MMapSessionManager session manager, it stores persistent session information in the SessionData directory. This cache has a Version file containing a version number that the server uses to determine the structure of the directories and files in the caches. You can clean out the caches by simply deleting the version file.
When the server starts up, if it does not find the version file, it deletes the directory structures for the corresponding caches and re-creates the version file. The next time the server serves a servlet while using MMapSessionManager session manager, it recreates the session data cache.
You can delete the version file simply by deleting it from the SessionData directory as you would normally delete a file, or you can use the Java>Delete Version Files page in the Server Manager to delete it. After deleting the version file, be sure to restart the iPlanet Web Server to force it to clean up the appropriate caches and to recreate the version file before the server serves any servlets.