NonStop Server for Java 4.2 Programmer's Reference

Java GC Profiling
The NonStop Server for Java 1.4.2 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 using HPjmeter. The -Xverbosegc option prints detailed information about the spaces within the Java
heap before and after the garbage collection.
The syntax to generate the output using this tool is:
-Xverbosegc[:help]|[0|1][:file=[stdout|stderr|<filename>]]
JVM Tuning Tools
PrintGCStats is a tool for mining verbose:gc logs that can aid analyzing and tuning garbage collection. You can
download this tool from the following location:
http://java.sun.com/developer/technicalArticles/Programming/turbo/PrintGCStats.zip
Additionally, for a discussion of profiling tools, see the Application Profiling section.
Tuning Application Performance
The topics are
Memory Considerations: Moving QIO to KSEG2●
Determining the Heap Manager●
Determining the Heap Setting●
Related Tuning Guides●
Memory Considerations: Moving QIO to KSEG2
Java server-side applications are typically configured with large Java heap sizes, in excess of 128 MB. In addition,
the JVM and its native components (for example, NonStop Servlets for JavaServer Pages (NSJSP) transport
library, JDBC Driver for SQL/MP, JDBC Driver for SQL/MX, SQL/MX call-level interface, and potentially any
custom-user JNI code) allocate memory for their own use. Thus, the overall heap space required by a JVM process
can be considerably higher than the configured Java heap space.
When a process uses the parallel TCP/IP transport provider for socket operations (like the iTP Secure WebServer
httpd daemon Server process instance), the process becomes a QIO client. For NonStop" Server QIO
shared-memory segments, when a QIO client process makes a socket request, a portion of the process address
space is reserved for the QIO segment. This reserved space limits the maximum useable heap size for the JVM
process.
The size of the QIO segment is determined by the configured physical memory for a processor (CPU) on the