NonStop Server for Java 6.0 Programmer's Reference

Sets the maximum size for the permanent generation. The default value for
MaxPermSize is 32 MB. The initial size of the permanent generation PermSize
option is ignored.
NOTE: At initialization time, the maximum size of the combined young and tenured
generations and the maximum size of permanent generation are allocated.
Implementation of Garbage Collector Types
The default garbage collectors in NonStop Server for Java 6.0 are:
• Copying collector for the young generation
• Mark-sweep collector for the tenured generation
NonStop Server for Java 6.0 uses these garbage collectors because they are the most efficient on
the NonStop system. A summary of garbage collector implementations appears in Table 7
(page 61). Paragraphs that follow discuss various implementations to help you understand
performance issues.
Table 7 Summary of Garbage Collector Implementations
Implementation StatusCollector Type
Default collector for the young generationCopying collector
Default collector for the tenured generationMark-sweep collector
Disabled“Parallel Collector” (page 61)
Disabled“Concurrent Low-Pause Collector”
(page 62)
Allowed“Incremental Low-Pause Collector”
(page 62)
Parallel Collector
The parallel collector (or throughput collector) uses the parallel version of the young generation
collector. The parallel collector is disabled in NonStop Server for Java 6.0 because this collector
applies only for Symmetric Multiprocessing (SMP) type machines. NonStop systems are not SMP
type machines.
The following java command options that specify a parallel collector or apply to a parallel collector
are not valid for NonStop Server for Java 6.0:
-XX:+UseParallelGC
Specifies a parallel garbage collector. If you specify this option, the JVM exits with
the error: -XX:+UseParallelGC option is not supported on this platform.
-XX:+UseParNewGC
Specifies a parallel garbage collection. This option is disabled. If you specify this
option, the JVM exits with the error: -XX:+UseParNewGC option is not supported
on this platform.
-XX:+UseAdaptiveSizePolicy
Specifies an adaptive size policy. This option applies only for a parallel collector
and, therefore, is disabled. If you specify this option, the JVM exits with the error:
-XX:+UseAdaptiveSizePolicy option is not supported on this platform.
-XX:+AggressiveHeap
Obtains the platform resources and configures the heap layout accordingly, uses
parallel collector, and enables AdaptiveSizePolicy option. This option applies
Garbage Collection (GC) 61