NonStop Server for Java 7.0 Programmer's Reference

However, using this option increases the application start up time, since the initialization of JVM
is slower.
HP recommends that a pilot run be conducted before deploying this option in production
environment. The objective of the pilot run is to ensure that the increase in the application start-up
time is tolerable, and that there is a visible reduction in the application stalls (pause times) during
GC. For more information, see “Application tuning and profiling” (page 86).
64–bit process support
NSJ7 allows creation of 64–bit Java processes. A 64–bit Java process can have a large Java
heap; the heap size can be greater than 1276 MB, which is the limit for 32–bit Java process. The
theoretical maximum Java heap size for a 64–bit Java process is 484 GB. However, the actual
limit is determined by the swap space configured, physical memory of the system, and number of
processes contending for these resources.
In 64–bit mode, the Java runtime environment performs marginally lower than it does in 32–bit
mode. This is due to the increase in the pointer sizes (8 bytes in 64–bit mode, and 4 bytes in
32–bit mode), which results in higher memory usage for the same set of operations compared to
32–bit mode, and hence lower performance.
The following sections describe how a 64–bit Java process can be launched:
• “-d64 option” (page 63)
• “Using 64–bit java launcher” (page 64)
-d64 option
This option can be used to launch a 64–bit Java process. To use this option, 64–bit JDK must be
installed along with the 32–bit JDK.
To launch a 64–bit Java process use the following steps:
1. Set the PATH environment variable to point to the 32–bit launcher using the following command
at the OSS prompt:
$ export PATH=/home/lee/nssjava/jdk170_h70/bin/:$PATH
2. Run the application using the 32–bit launcher and —d64 option:
java -d64 <application_classname>
Launching a 64–bit Java process using —d64 option has the following limitations:
• 64–bit process cannot not be launched as a named process. For more information, see “Java
process name” (page 98).
• 64–bit process cannot be launched inside the Native Inspect (eInspect) debugger, see
“Debugging Java process” (page 99).
To overcome these limitations, you must launch the 64–bit Java process as described in “Using
64–bit java launcher” (page 64).
If —d64 option is used with any previous NonStop Java versions, the following error
message is displayed on stdout and the application exits:
Running a 64–bit JVM is not supported on this platform.
If –d64 option is used with 32–bit version of NSJ7, and 64–bit version of NSJ7 is
not installed, then the following error message is displayed:
This Java instance does not support a 64–bit JVM. Please Install the
64–bit JDK.
NOTE: If application uses user library then _RLD_LIB_PATH must point to a 64–bit User Library.
64–bit process support 63