NonStop Server for Java 4.2 Programmer's Reference

Segment Size........... 134217728

MDs in Use............. 1248

Max MDs Used........... 2357

Last Fail Size......... 0

Current Pool Size...... 16774788 Initial Pool Size...... 16776992

Max Pool Size.......... 16776992 Min Pool Size.......... 16776992

Current Pool Alloc..... 4516992 Max Pool Alloc......... 4715520

Current Pool Frags..... 375 Max Pool Frags......... 382

The QIO segments on this system (\GOBLIN) have been moved to KSEG2 based on the value of the segment type.

The value is RESIDENT if QIO is moved to KSEG2.

The first SCF output for \NAVAE1 shows QIO to be in FLAT_UA, which means that QIO has not been moved to

KSEG2.

Determining the Heap Manager

The C Runtime Heap manager (T1269) offers a substantial performance boost over the older heap manager

(T8431). While this performance boost might not affect any pure Java code, the JVM contains native (C and C++)

code; therefore, using the T1269 heap manager will boost the JVM performance.

To find the C Runtime Heap Manager being used on your NonStop system, use the vproc command output from

the ZCRESRL library; at the TACL prompt, type.

TACL> vproc $SYSTEM.sysnn.ZCRESRL

Where sysnn is the system number.

Determining the Heap Setting

You should set the Java heap to a value appropriate for your application. For most application-server

environments, the heap size is set high to optimize performance. This size can be more than 256 MB (after QIO

has been moved to KSEG2).

To study the frequency and length of the JVM Garbage Collection operation, use the -verbose:gc option in the

JVM arguments. Then use this data to tune the heap usage of the JVM based on your application requirements.

Note: The JVM allocates the maximum required heap for the JVM usage at startup, so the swap space

considerations for the JVM process are the maximum Java heap space specified in addition to other

JVM memory requirements and the memory requirements for all native components.

To identify the swap usage of a process or the swap requirements for a CPU, use the NSKCOM utility. For

example, to identify the swap usage of all the processes or a particular process, enter the following commands at

the OSS prompt. Sample NSKCOM output follows the command line.

$ gtacl p nskcom

NSKCOM - T5838G05 BASE (22JUL02) - Nov 5 2002

$SYSTEM.SYSTEM.ZSYSCFG

KMS.SWAPFILE = 0 $DATA03.SWAP.CPU0A STOP