NonStop Server for Java 7.0 Programmer's Reference

NOTE: You must consider the amount of physical memory available on the system while choosing
a value for —Xmx. If the virtual memory of a process exceeds the physical memory, then memory
thrashing occurs and the application performance slows down.
NOTE: HP recommends that the application specifies the same value for —Xms and —Xmx. If only
—Xmx is specified in the command-line, the default value used for —Xms is the same value that is
specified for —Xmx.
-XX:MaxPermSize
Sets the maximum size for the permanent generation. The default value for
MaxPermSize is 64 MB for both 32–bit and 64–bit NSJ7. 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 maximum size of permanent generation are allocated.
Implementation of garbage collector types
The available garbage collectors in NSJ7 are as follows:
• Serial collector (default collector for young and tenured generations)
• Parallel collector
• Parallel compacting collector
• Concurrent Mark-Sweep collector (or Concurrent low-pause collector)
Table 7 Summary of garbage collector implementations
Implementation StatusCollector Type
Default collector for the young and tenured generationSerial collector
Allowed“Parallel collector” (page 53)
Allowed“Concurrent Low-Pause collector”
(page 54)
Parallel collector
The parallel collector (or throughput collector) uses the parallel version of the young generation
collector. The parallel collector is available only for J-series systems.
NOTE: To enable the appropriate GC, use the "+" option. To disable the appropriate GC, use
the "—" option.
The following are the valid java command options, that specify or apply to a parallel collector:
-XX:+UseParallelGC
This option enables parallel scavenge for the young generation.
NOTE: The default GC is the serial GC.
-XX:+UseParNewGC
This option enables new parallel scavenge for the young generation. The difference
between parallel GC and ParNewGC is that ParNewGC is optimized for use with
CMS GC. This is the default scavenge GC if CMS GC is specified.
-XX:+UseParallelOldGC
Garbage collection (GC) 53