NonStop Server for Java 6.0 Programmer's Reference

NOTE:
• As described earlier, the NonStop Server for Java 6.0 does not support the throughput collector
(specified with the option –XX:+UseParallelGC) or the concurrent low pause collector
(specified with the option –XX:+UseConcMarkSweepGC).
• Also, the following options do not apply either for the NonStop Server for Java 6.0 or the
NonStopsystem:
-XX:+UseBoundThreads — Option to bind user level threads; Solaris specific
-XX:+UseAltSigs — Solaris specific.
-XX:+UseV8InstrsOnly — Only for Sparc (Solaris)
-XX:-AllowUserSignalHandlers — Solaris specific
-XX:AltStackSize=nn — Solaris specific
-XX:+MaxFDLimit — Solaris specific
-XX:-UseBoundThreads — Solaris specific
-XX:-UseLWPSynchronization — Solaris specific
-XX:PreBlockSpin=nn — Only for Linux
-XX:-UseISM — Solaris specific
-XX:-UseMPSS — Solaris specific
-XX:-UseSpinning — Only for Linux
Java GC Profiling
The NonStop Server for Java 6.0 supports an HP proprietary option, -Xverbosegc to capture
the java application's GC activity. The output of this tool can be used to view and analyze the
detailed statistics in an offline mode with HPjmeter. The -Xverbosegc option prints out detailed
information about the spaces within the Java Heap before and after the garbage collection.
The syntax :
-Xverbosegc[:help]|[0|1][:file=[stdout|stderr|<filename>]]
Fore more information on the syntax options of -Xverbosegc, see java in the NonStop Server
for Java 6.0 Tools Reference Pages.
HeapDumpOnly option
The -XX:+HeapDump option can be used to observe memory allocation in a running Java application
by taking snapshots of the heap over time.
Another way to get heap dumps is to use the _JAVA_HEAPDUMP environment variable; setting this
environment variable enables you to take memory snapshots without making any modifications to
the Java command line. To enable this functionality, either use the command line option or set the
environment variable (for example, export _JAVA_HEAPDUMP=1) before starting the Java
application.
The HeapDumpOnly log contains only the heap dump and not the thread stack trace dump. If
required, you can use the –Xrunhprof:heap=dump option to produce a log that contains both
the heap dump and thread stack trace dump.
With the -XX:+HeapDump option enabled, each time the process is sent a SIGQUIT signal, the
Java VM produces a snapshot of the Java heap in hprof ASCII format:
java_<pid>_<date>_<time>_heapDump.hprof.txt.
If you set the _JAVA_HEAPDUMP_ONLY option, heap dumps are triggered by SIGWINCH instead
of SIGQUIT. Only the heap dump is produced; that is, the thread and trace dump of the application
64 Implementation Specifics