Access Manager Cache and Sessions

The performance of a portal system is affected to a large extent by the cache hit ratio of the Access Manager cache. This cache is highly tunable, but a trade-off exists between memory used by this cache and the available memory in the rest of the heap.

You can enable the amSDKStats logs to monitor the number of active sessions on the server and the efficiency of the Directory Server cache. These logs are located by default in the /var/opt/SUNWam/stats directory. Use the com.iplanet.am.stats.interval parameter to set the logging interval. Do not use a value less than five (5) seconds. Values of 30 to 60 seconds give good output without impacting performance.

The com.iplanet.services.stats.directory parameter specifies the log location, whether to a file or to the Portal Server administration console, and also is used to turn off the logs. You must restart the server for changes to take effect. Logs are not created until the system detects activity.

Multiple web container instances write logs to the same file.

The cache hit ratio displayed in the amSDKStats file gives both an internal value and an overall value since the server was started. Once a user logs in, the user’s session information remains in cache indefinitely or until the cache is filled up. When the cache is full, oldest entries are removed first. If the server has not needed to remove a user’s entry, it might be the case that on a subsequent login—days later, for example—the user’s information is retrieved from the cache. Much better performance occurs with high hit ratios. A hit ratio of a minimum of 80 percent is a good target although (if possible) an even higher ratio is desired.