NonStop Server for Java 6.0 Programmer's Reference

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

(-Xverbosegc) 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

KMS.SWAPFILE = 0 $DATA03.SWAP.CPU0B STOP

KMS.SWAPFILE = 5 $SWAP45.SWAP4.CPU05

NSK-status swap-usage 1,423 ,detail

SYSTEM : \GOBLIN LOGTIME : March 19, 2004 02:50:29

TYPE : (E=Extensible S=Shared O=Owner)

(CPU Page size is 16384 Bytes)

Program File NameUser-IDPriProcess

$DATA11.ZYQ0000T.Z00001VH103,431551,423$JSV1

68 Implementation Specifics