IBM SDK for z/OS, Java Technology Edition Version 7 SDK and Runtime Guide IBM SDK for z/OS, Java Technology Edition Version 7 SDK and Runtime Guide Note Before using this information and the product it supports, read the information in “Notices” on page 481. Copyright information This edition of the user guide applies to the IBM 31-bit SDK for z/OS, Java Technology Edition, Version 7, product 5655-I98, and to the IBM 64-bit SDK for z/OS, Java Technology Edition, Version 7, product 5655-I99, and to all subsequent releases, modifications, and Service Refreshes, until otherwise indicated in new editions. Portions © Copyright 1997, 2013, Oracle and/or its affiliates. © Copyright IBM Corporation 2011, 2013. US Government Users Restricted Rights – Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp. Contents Preface ...............v RMI-IIOP limitations ..........66 Further reading ............66 Chapter 1. Product overview ......1 Examples of client–server applications ....66 Using the ORB ............72 Introduction to Java ............1 How the ORB works ..........75 IBM Software Developers Kit (SDK) .....1 Additional features of the ORB .......82 IBM Java Runtime Environment (JRE) .....4 The Java Native Interface (JNI) ........88 IBM Java Virtual Machine (JVM).......5 Overview of JNI ............89 What's new ...............6 The JNI and the Garbage Collector .....90 IBM J9 Virtual Machine ..........6 Copying and pinning ..........94 Memory management ..........11 Handling exceptions ..........96 Class data sharing ...........12 Synchronization ............96 The JIT compiler............13 Debugging the JNI ...........97 Diagnostic component ..........13 JNI checklist .............99 Conventions and terminology ........16 Other sources of information ........17 Accessibility ..............18 Chapter 3. Planning.........101 Migrating from earlier IBM SDK or JREs ....101 Chapter 2. Understanding the IBM Version compatibility ...........102 Software Developers Kit (SDK) for Java 19 Supported environments .........102 The building blocks of the IBM Virtual Machine for Chapter 4. Installing and configuring Java .................19 Java application stack ..........20 theSDK..............105 Components of the IBM Virtual Machine for Java 21 Working with BPXPRM settings .......105 Memory management ...........23 Setting the region size ..........106 Overview of memory management .....23 Setting MEMLIMIT ...........106 Allocation ..............26 Setting LE runtime options .........106 Detailed description of global garbage collection 29 Setting LE 31-bit runtime options......107 Generational Concurrent Garbage Collector. 37 Setting LE 64-bit runtime options......108 Balanced Garbage Collection policy .....39 Marking failures ............108 How to do heap sizing .........45 Setting the path ............108 Interaction of the Garbage Collector with Setting the class path ...........109 applications .............46 Updating your SDK or JRE for daylight saving How to coexist with the Garbage Collector . 47 time changes .............109 Frequently asked questions about the Garbage Running the JVM under a different code page . 110 Collector ..............50 Using non-default system fonts .......111 Class loading ..............53 The parent-delegation model .......53 Chapter 5. Developing Java Namespaces and the runtime package ....54 applications ............113 Custom class loaders ..........54 Using XML ..............113 Class data sharing ............55 Migrating to the XL-TXE-J ........115 The JIT compiler.............57 | Securing JAXP processing against malformed JIT compiler overview ..........57 || input ...............117 How the JIT compiler optimizes code.....58 XML reference information ........117 Frequently asked questions about the JIT Debugging Java applications ........122 compiler ..............59 Java Debugger (JDB) ..........122 The AOT compiler ............60 Determining whether your application is running Java Remote Method Invocation .......61 on a 31-bit or 64-bit JVM .........123 The RMI implementation .........61 How the JVM processes signals .......124 Thread pooling for RMI connection handlers . 62 Signals used by the JVM ........124 Understanding distributed garbage collection . 63 Linking a native code driver to the Debugging applications involving RMI ....63 signal-chaining library .........126 TheORB...............64 Writing JNI applications ..........127 CORBA...............64 Supported compilers ..........128 RMI and RMI-IIOP ...........65 Native formatting of Java types long, double, Java IDL or RMI-IIOP? .........65 float ...............128 © Copyright IBM Corp. 2011, 2013 iii Support for thread-level recovery of blocked First steps in problem determination ....174 connectors ..............129 z/OS problem determination .......175 CORBA support ............129 NLS problem determination .......194 System properties for tracing the ORB ....130 ORB problem determination .......196 System properties for tuning the ORB ....131 Attach API problem determination .....209 Java security permissions for the ORB ....131 Using diagnostic tools ..........212 ORB implementation classes .......132 Overview of the available diagnostic tools. 212 RMI over IIOP .............132 Using the IBM Monitoring and Diagnostic Tools RMI-IIOP Programmer's Guide ......133 for Java ..............219 Implementing the Connection Handler Pool for Using dump agents ..........221 RMI................140 Using Javadump ...........240 Enhanced BigDecimal ..........140 Using Heapdump ...........262 Working in a multiple network stack environment 140 Using system dumps and the dump viewer . 271 Support for XToolkit ...........141 Tracing Java applications and the JVM ....288 Support for the Java Attach API .......141 JIT and AOT problem determination ....322 The Diagnostics Collector ........328 Chapter 6. Running Java applications 145 Garbage Collector diagnostic data .....333 The java and javaw commands .......145 Class-loader diagnostic data .......341 Obtaining version information.......145 Shared classes diagnostic data .......344 Specifying Java options and system properties 146 Using the Reliability, Availability, and Standard options ...........147 Serviceability Interface .........372 Globalization of the java command .....148 Using the HPROF Profiler ........385 The Just-In-Time (JIT) compiler .......149 Using the JVMTI ...........389 Disabling the JIT ...........149 Using the Diagnostic Tool Framework for Java 405 Enabling the JIT ...........149 Using JConsole ............412 Determining whether the JIT is enabled . 150 Specifying a garbage collection policy .....150 Chapter 10. Reference .......417 Garbage collection options ........151 Command-line options ..........417 More effective heap usage using compressed Specifying command-line options......417 references .............151 General command-line options ......418 Pause time .............152 System property command-line options . 419 Pause time reduction ..........152 JVM command-line options........428 Environments with very full heaps .....153 JVM -XX command-line options ......446 || Euro symbol support ...........154 JIT and AOT command-line options .....448 || Configuring large page memory allocation . 154 Garbage Collector command-line options . 453 Balanced Garbage Collection policy options . 464 Chapter 7. Performance .......157 JVM messages .............465 Class data sharing between JVMs ......157 Finding logged messages ........466 Overview of class data sharing ......157 Obtaining detailed message descriptions . 466 Class data sharing command-line options . 159 CORBA minor codes ...........467 Creating, populating, monitoring, and deleting a Environment variables ..........469 cache ...............165 Displaying the current environment .....469 Performance and memory consumption . 166 Setting an environment variable ......469 Considerations and limitations of using class Separating values in a list ........469 data sharing .............166 JVM environment settings ........470 Adapting custom class loaders to share classes 168 z/OS environment variables .......473 Performance problems ..........169 Default settings for the JVM ........474 Known issues and limitations ........476 Chapter 8. Security .........171 Support for virtualization software ......479 Notices ..............481 Chapter 9. Troubleshooting and Privacy Policy Considerations ........483 support ..............173 Trademarks ..............483 Submitting problem reports ........173 Problem determination ..........173 iv IBM SDK for Java: SDK and Runtime Guide Preface This user guide provides general information about the IBM® SDK for z/OS®, Java™ Technology Edition, Version 7. The guide gives specific information about any differences in the IBM implementation compared with the Oracle implementation. This user guide applies to IBM SDK for z/OS, Java Technology Edition, Version 7. Read this user guide with the more extensive documentation on the Oracle Web site: http://www.oracle.com/technetwork/java/index.html. The terms Runtime Environment and Java Virtual Machine are used interchangeably throughout this user guide. The Program Code is not designed or intended for use in real-time applications such as (but not limited to) the online control of aircraft, air traffic, aircraft navigation, or aircraft communications; or in the design, construction, operation, or maintenance of any nuclear facility. © Copyright IBM Corp. 2011, 2013 v vi IBM SDK for Java: SDK and Runtime