IBM BS029ML - WebSphere Portal Server Self Help Manual page 160

As the Portal Server places a greater demand on JVM memory, you should increase the Java
minimum and maximum heap sizes accordingly.
To view or modify the SUN JVM settings from the WebSphere Application Server
Administrative Console, select Servers → Application Servers → WebSphere_Portal →
Server Infrastructure → Java and Process Management → Process Definition → Java
Virtual Machine. Table 5-3 shows the default and recommended values.
Table 5-3 SUN JVM settings
Parameter
JVM initial heap size
JVM maximum heap size
Additional SUN JVM attributes
For the SUN JVM, we strongly recommend that you set a number of additional JVM attributes
to fine-tune the behavior of the generational heap. Increase the size of the Young generation
heap (NewSize and MaxNewSize), as objects in this heap should not live through more then
one garbage collection (GC) cycle. Up to 50% to 60% of the total heap size can be set for the
Young generation. Also, consider slightly increasing SurvivorRatio.
Additionally, ensure that the Permanent generation (PermSize and MaxPermSize) is
adequately sized to hold all class loaded data. This includes classes loaded at Portal Server
runtime startup and dynamically compiled JSPs. If the Permanent generation becomes full, a
Full GC will result.
Note: The Permanent generation is not allocated from the heap defined by either the
(-Xms) or (-Xmx) settings.
To view or modify the SUN JVM settings from the WebSphere Application Server
Administrative Console, select Servers → Application Servers → WebSphere_Portal →
Server Infrastructure → Java and Process Management → Process Definition → Java
Virtual Machine. Table 5-4 shows the default and recommended values.
Table 5-4 Additional SUN JVM settings
Parameter
HotSpot Server option
Default size of New Generation (in bytes)
Maximum size of New Generation (in bytes).
Default size of Permanent Generation
Maximum Permanent Generation Size
Ratio of Eden / Survivor Space Size
GC Concurrent Collector
GC Parallel Collector
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IBM WebSphere Portal V6 Self Help Guide
Default value
n/a
n/a
Default value
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Recommended value
1536
2048
Recommended value
-server
-XX:NewSize=(50% to
60% of heap)
-XX:MaxNewSize=(50%
to 60% of heap)
-XX:PermSize=512m
-XX:MaxPermSize=768
m
-XX:SurvivorRatio=16
-XX:
+UseConcMarkSweep
GC
-XX:+UseParNewGC