Note: Before using this information and the product it supports, be sure to read the general information under Notices.
This edition of the User Guide applies to the IBM 64-bit Runtime Environment for Windows on Intel Itanium architecture, Java 2 Technology Edition, Version 1.4.2, and to all subsequent releases, modifications, and service refreshes, until otherwise indicated in new editions.
(C) Copyright Sun Microsystems, Inc. 1997, 2003, 901 San Antonio Rd., Palo Alto, CA 94303 USA. All rights reserved.
(C) Copyright International Business Machines Corporation, 1999, 2007. All rights reserved.
U.S. Government Users Restricted Rights - Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp.
The IBM(R) 64-bit Runtime Environment for Windows(R) on Intel(R) Itanium(R) architecture, Java(TM) 2 Technology Edition, Version 1.4.2 contains the Java(TM) Virtual Machine (JVM), core Sun Microsystems Java classes, and supporting files. The Runtime Environment does not contain all the classes that are found in the SDK package.
The User Guide provides general information about the Runtime Environment and specific information about any differences in the IBM(R) implementation of the Runtime Environment compared with the Sun implementation. Read this User Guide in conjunction with the more extensive documentation on the Sun Web site: http://java.sun.com.
The Runtime Environment is supported on Microsoft(R) Windows(R) XP 64-Bit Edition and Windows Server 2003 64-bit edition.
The IBM JVM Diagnostics Guide provides more detailed information about the IBM JVM.
Note that the Runtime Environment for Windows is a subset of the SDK and enables you only to run Java applications. If you have installed the SDK, the Runtime Environment is included.
The terms "Runtime Environment" and "Java Virtual Machine" are used interchangeably throughout this User Guide.
Technical changes made to this User Guide for Version 1.4.2, other than minor or obvious ones such as updating "1.4.1" to "1.4.2", are indicated in red when viewing in HTML or in a color-printed copy and by vertical bars to the left of the changes.
There is no guarantee that 1.4.2-compiled classes will work on pre-1.4.0 Runtime Environment releases.
To obtain the IBM build and version number, at a command prompt type:
java -version
The just-in-time (JIT) compiler (jitc.dll) dynamically generates machine code for frequently used bytecode sequences in Java applications and applets while they are running.
The Runtime Environment for Windows includes the JIT (jitc.dll), which is enabled by default. You can disable the JIT to help isolate a problem with a Java application, an applet, or the compiler itself.
To disable the JIT, at a command prompt in the window where you will run the application, type:
set JAVA_COMPILER=NONE
To enable the JIT, type at a command prompt:
set JAVA_COMPILER=jitc
To verify whether or not the JIT is enabled, type at a command prompt:
java -version
If the JIT is in use, a message is displayed that includes:
(JIT enabled: jitc)
If the JIT is not in use, a message is displayed that includes:
(JIT disabled)
The java tool launches a Java application.
The JVM searches for the startup class, and other classes that are used, in three sets of locations: the bootstrap classpath, the installed extensions, and the user classpath. Arguments after the class name or JAR file name are passed to the main function.
The javaw command is identical to java, except that javaw has no associated console window. Use javaw when you do not want a command prompt window to appear. The javaw launcher displays a dialog box with error information if a launch fails.
The java and javaw command have the following syntax:
java [ options ] class [ arguments ... ] java [ options ] -jar file.jar [ arguments ... ] javaw [ options ] class [ arguments ... ] javaw [ options ] -jar file.jar [ arguments ... ]
Items that are within brackets are optional.
If the -jar option is specified, the named .jar file contains class and resource files for the application, with the startup class indicated by the Main-Class manifest header.
From Version 1.4.2 Service Refresh 4, using the -jar command-line option will make the .jar file the source of all user classes; all other user CLASSPATH settings will be ignored.
To be able to use a .jar file with other CLASSPATH settings, add the .jar file to the CLASSPATH as above, and specify the startup class manually.
The launcher has a set of standard options that are supported on the current runtime environment and will be supported in future releases. In addition, there is a set of nonstandard options.
The -X options listed below are a subset of the available ones. They are nonstandard and subject to change without notice.
If you specify the arguments X and Y (both are integers), the verboseGC output is redirected to X number of files, each containing Y number of GC cycles worth of verboseGC output. |Filename must contain a "#" |(hash symbol), which is substituted with a generation identifier, starting |at 1. These files have the form filename1, filename2, and so on.
The java command and other java launcher commands (such as javaw) allow a class name to be specified as any character that is in the character set of the current locale.
You can specify any Unicode character in the class name and arguments by using java escape sequences. To do this, you must specify -Xargencoding. To specify a Unicode character, use escape sequences in the form \u####, where # is a hexadecimal digit (0 through 9, A through F).
To specify that the class name and command arguments are in UTF8 or ISO8859_1 encoding, use -Xargencoding:utf8 and -Xargencoding:latin.
In the Runtime Environment, if you are using a non-English locale, the java and javaw commands give translated output messages. These messages are different from those that were in the 1.3.1 version and also differ based on the locale in which Java is running. The detailed error descriptions and other debug information that is returned by java is in English. Debug information that is returned during initialization is shown in brackets.
In the Runtime Environment, you can specify a class name as a complete file name including a full path and the .class extension. In previous versions of the SDK, you could specify only the class that was relative to the CLASSPATH, and the .class extension was not allowed. Use of the complete file name permits you to launch a java application from your desktop or file launcher. If you specify a .class file with path and extension, the specified path is put into the CLASSPATH. For example, the command java c:\myapp\thisapp.class is equivalent to specifying java -classpath c:\myapp thisapp.
From Version 1.4.2 Service Refresh 4, using the -jar command-line option will disable the use of a CLASSPATH.
To set a java class or jar file to execute automatically from the file use Tools->Folder Options->File Type option of Windows Explorer. Alternatively, at a command prompt type:
assoc .class=javaclass ftype javaclass=C:\Program Files\IBM\Java142\jre\bin\java.exe %l %*
You can set the system property ibm.jvm.bootclasspath by using the -D option that is described in Launching a Java application. The value of this property is used as an additional search path, which is inserted between any value that is defined by -Xbootclasspath/p: and the bootstrap classpath. The bootstrap classpath is either the default, or that is defined using the -Xbootclasspath: option.
Do not deploy applications that use the -Xbootclasspath: or -Xbootclasspath/p: option to override a class in core.jar, graphics.jar, server.jar, security.jar, xml.jar, tools.jar, or charsets.jar, because such a deployment would contravene the Java 2 Runtime Environment binary code license.
The -Xgcpolicy JVM runtime option specifies garbage collection policy.
-Xgcpolicy takes the values optthruput (the default) or optavgpause. The option controls garbage collector behavior, making tradeoffs between throughput of the application and overall system and the pause times that are caused by garbage collection.
The format of the option and its values is:
-Xgcpolicy:optthruput
-Xgcpolicy:optavgpause
When an application's attempt to create an object cannot be satisfied immediately from the available space in the heap, the garbage collector is responsible for identifying unreferenced objects (garbage), deleting them, and returning the heap to a state in which the immediate and subsequent allocation requests can be satisfied quickly. Such garbage collection cycles introduce occasional unexpected pauses in the execution of application code. Because applications grow in size and complexity, and heaps become correspondingly larger, this garbage collection pause time tends to grow in size and significance. The default garbage collection value, optthruput, delivers very high throughput to applications, but at the cost of these occasional pauses, which can vary from a few milliseconds to many seconds, depending on the size of the heap and the quantity of garbage.
The optavgpause option substantially reduces the time that is spent in these garbage collection pauses, in addition to limiting the effect of increasing heap size on the length of the garbage collection pause. This option is particularly relevant to configurations that have large heaps. The pause times are reduced by performing some garbage collection activities that are concurrent with normal program execution. With the reduced pause time, you might experience some reduction of application throughput, which varies from application to application.
If the Java heap becomes nearly full, and very little garbage is to be reclaimed, requests for new objects might not be satisfied quickly because no space is immediately available. If the heap is operated at near-full capacity, application performance might suffer regardless of which of the above options is used; and, if requests for more heap space continue to be made, the application receives an OutofMemory exception, which results in JVM termination if the exception is not caught and handled. At this point the JVM will produce two diagnostic files: a Heapdump and a Javadump. These are detailed in the Diagnostics Guide for Java v1.4.2 and can be used to determine what caused the high occupancy of the Java heap. The Diagnostics Guide is on developerWorks(R), at: http://www-106.ibm.com/developerworks/java/jdk/diagnosis/. In these conditions, you are recommended either to increase the heap size by using the -Xmx option, or to reduce the number of application objects in use.
For more detailed information about garbage collection, see:
http://www.ibm.com/developerworks/ibm/library/i-garbage1/
http://www.ibm.com/developerworks/ibm/library/i-garbage2/
http://www.ibm.com/developerworks/ibm/library/i-garbage3/
| | |Thread pooling for RMI Connection Handlers is not enabled |by default.
|To enable the connection pooling implemented at the RMI TCPTransport level, |set the option
|-Dsun.rmi.transport.tcp.connectionPool=true (or any non-null value)|
This version of the Runtime Environment does not have any setting that |you can use to limit the number of threads in the connection pool.
When a signal is raised that is of interest to the JVM, a signal handler is called. This signal handler determines whether it has been called for a Java or non-Java thread. If the signal is for a Java thread, the JVM takes control of the signal handling. If the signal is for a non-Java thread, and the application that installed the JVM had previously installed its own handler for the signal, control is given to that handler. Otherwise, the signal is ignored (whether or not this is not the signal's default action). The exception to this rule is on Windows, where for a signal generated externally (for example, when you enter CTRL-C or CTRL-BREAK) a new thread is created to execute the signal handler. In this case, the JVM signal handler assumes that the signal is for the JVM.
For exception and error signals the JVM either:
For interrupt signals, the JVM also enters a controlled shutdown sequence, but this time it is treated as a normal termination that:
The shutdown is identical to the shutdown initiated by a call to the Java method System.exit().
Other signals that are used by the JVM are for internal control purposes and do not cause it to terminate. The only control signal of interest is SIGBREAK, which causes a Javadump to be generated.
Table 1 below shows the signals that are used by the JVM. The signals have been grouped in the table by type or use, as follows:
Signal Name | Signal type | Description | Disabled by -Xrs |
---|---|---|---|
SIGSEGV | Exception | Incorrect access to memory (write to inaccessible memory) | No |
SIGILL | Exception | Illegal instruction (attempt to invoke an unknown machine instruction) | No |
SIGFPE | Exception | Floating point exception (divide by zero) | No |
SIGABRT | Error | Abnormal termination. The JVM raises this signal whenever it detects a JVM fault. | Yes |
SIGINT | Interrupt | Interactive attention (CTRL-C). JVM exits normally. | Yes |
SIGTERM | Interrupt | Termination request. JVM will exit normally. | Yes |
SIGBREAK | Control | A break signal from a terminal. JVM uses this for taking Javadumps. | Yes |
Use the -Xrs (reduce signal usage) option to prevent the JVM from handling most signals. For more information, see Sun's Java application launcher page at http://java.sun.com/j2se/1.4.2/docs/tooldocs/windows/java.html.
Signals 2 (SIGINT), 4 (SIGILL), 6 (SIGABRT), 8 (SIGFPE), 11 (SIGSEGV), and 15 (SIGTERM) cause the JVM to shut down; therefore, an application signal handler should not attempt to recover from these unless it no longer requires the services of the JVM.
The Runtime Environment contains a signal-chaining facility. Signal-chaining enables the JVM to interoperate more efficiently with native code that installs its own signal handlers.
The signal-chaining facility enables an application to link and load the shared library jsig.dll before msvcrt.dll. The jsig.dll library ensures that calls to signal() are intercepted so that their handlers do not replace the JVM's signal handlers. Instead, these calls save the new signal handlers, or "chain" them behind the handlers that are installed by the JVM. Later, when any of these signals are raised and found not to be targeted at the JVM, the preinstalled handlers are invoked.
To use jsig.dll, link it with the application that creates or embeds a JVM.
When working with an Input Method Editor (IME), you are advised that character composition should be completed and the candidate selected before using the workspace for any other operation.
If you are a user of Traditional Chinese, you should not pipe the output from your Java application directly into the more command. Instead, direct the output to a temporary file and then view the file separately.
If you have any comments about the usefulness, or otherwise, of this User Guide, we would be pleased to hear from you through one of these channels. Please note that these channels are not set up to answer technical queries, but are for comments about the documentation only. Send your comments:
The fine print. By choosing to send a message to IBM, you acknowledge that all information contained in your message, including feedback data, such as questions, comments, suggestions, or the like, shall be deemed to be non-confidential and IBM shall have no obligation of any kind with respect to such information and shall be free to reproduce, use, disclose, and distribute the information to others without limitation. Further, IBM shall be free to use any ideas, concepts, know-how or techniques contained in such information for any purpose whatsoever, including, but not limited to, developing, manufacturing and marketing products incorporating such information.
This information was developed for products and services offered in the U.S.A. IBM may not offer the products, services, or features discussed in this document in other countries. Consult your local IBM representative for information on the products and services currently available in your area. Any reference to an IBM product, program, or service is not intended to state or imply that only that IBM product, program, or service may be used. Any functionally equivalent product, program, or service that does not infringe any IBM intellectual property right may be used instead. However, it is the user's responsibility to evaluate and verify the operation of any non-IBM product, program, or service.
IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to:
For license inquiries regarding double-byte (DBCS) information, contact the IBM Intellectual Property Department in your country or send inquiries, in writing, to:
The following paragraph does not apply to the United Kingdom or any other country where such provisions are inconsistent with local law:
INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer of express or implied warranties in certain transactions, therefore, this statement may not apply to you.
This information could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the information. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this information at any time without notice.
Any references in this information to non-IBM Web sites are provided for convenience only and do not in any manner serve as an endorsement of those Web sites. The materials at those Web sites are not part of the materials for this IBM product and use of those Web sites is at your own risk.
IBM may use or distribute any of the information you supply in any way it believes appropriate without incurring any obligation to you.
Licensees of this program who wish to have information about it for the purpose of enabling (i) the exchange of information between independently created programs and other programs (including this one) and (ii) the mutual use of the information which has been exchanged, should contact:
Such information may be available, subject to appropriate terms and conditions, including in some cases, payment of a fee.
The licensed program described in this document and all licensed material available for it are provided by IBM under terms of the IBM Customer Agreement, IBM International Program License Agreement or any equivalent agreement between us.
Any performance data contained herein was determined in a controlled environment. Therefore, the results obtained in other operating environments may vary significantly. Some measurements may have been made on development-level systems and there is no guarantee that these measurements will be the same on generally available systems. Furthermore, some measurement may have been estimated through extrapolation. Actual results may vary. Users of this document should verify the applicable data for their specific environment.
Information concerning non-IBM products was obtained from the suppliers of those products, their published announcements or other publicly available sources. IBM has not tested those products and cannot confirm the accuracy of performance, compatibility or any other claims related to non-IBM products. Questions on the capabilities of non-IBM products should be addressed to the suppliers of those products.
IBM and developerWorks are trademarks or registered trademarks of International Business Machines Corporation in the United States, or other countries, or both.
Java and all Java-based trademarks are trademarks of Sun Microsystems, Inc. in the United States, other countries, or both.
Microsoft, Windows, Windows NT, and the Windows logo are trademarks of Microsoft Corporation in the United States, other countries, or both.
Other company, product, or service names may be trademarks or service marks of others.
This product includes software developed by the Apache Software Foundation http://www.apache.org/.