Tuning Suggestions:

At the startup of the jvm the Xmx memory is pre-allocated. So by monitoring the usage of the jvm we can set the Xmx properly. Change the 2Gb Xmx settings to 1 Gb. When I was on the machine earlier there was no jvm taking more then 256Mb. This means we should be able to change all of them to 512Mb and be fine. As I mentioned before we only need to have large heap settings when we actually do a stress test but not for normal processing. Make these changes and bounce all the jvms. See Red below.

The native and Java heaps The JVM maintains two memory areas, the Java heap, and the native (or system) heap. These two heaps have different purposes and are maintained by different mechanisms. The Java heap contains the instances of Java objects and is often referred to simply as 'the heap'. It is the Java heap that is maintained by Garbage Collection, and it is the Java heap that is changed by the command-line heap settings. The Java heap is allocated using mmap, or shmat if large page support is requested. The maximum size of the Java heap is preallocated during JVM startup as one contiguous area, even if the minimum heap size setting is lower. This allocation allows the artificial heap size limit imposed by the minimum heap size setting to move toward the actual heap size limit with heap expansion. See Understanding the Garbage Collector for more information.

Note: You must have a system preferences directory when working with the Java viewer toolkit on UNIX-based systems

Symptom

You receive the following warnings:

IFVTE /u/IFVTE/usr/lpp/icm/V8R3M0/samples/java/viewer:>java TGenericDocViewer Jun 6, 2005 6:53:41 PM java.util.prefs.FileSystemPreferences$3 run WARNING: Could not create system preferences directory. System preferences are unusable. Jun 6, 2005 6:54:12 PM java.util.prefs.FileSystemPreferences checkLockFile0ErrorCode WARNING: Could not lock System prefs. Unix error code 1024. Jun 6, 2005 6:54:42 PM java.util.prefs.FileSystemPreferences checkLockFile0ErrorCode

Possible cause

The default system preferences directory did not get created and the warning messages are going into the Java console when running an application with the Java viewer toolkit.

Action

The preferences default implementation on UNIX-based operating systems is to use java.util.prefs.FileSystemPreferences and that utility uses properties to determine where to place the following preferences: java.util.prefs.systemRoot (default /etc/.java/.systemPrefs) java.util.prefs.userRoot (default System.getProperty(“user.home”) + “.userPrefs”)

An administrator with root access must create the system preferences directory /etc/.java/.systemPrefs with drwxr-xr-x access.