JavaTM 2, Standard Edition, v. 1.3.0_02
for Caldera® UNIX® Operating Systems
The Java 2 Standard Edition contains both the Java 2 Runtime Environment, which allows Caldera UNIX end users to run Java applets and applications on Caldera UNIX operating systems, and the Java 2 Software Development Kit (J2SDK), which enables Caldera UNIX OEMs, ISVs, and end users to develop Java applets and applications that conform to the Java 2 Core API.
This product is hereafter referred to as either "J2SE 1.3 for Caldera UNIX" or "J2SDK 1.3 for Caldera UNIX", depending upon which context the reference occurs in.
J2SE 1.3 for Caldera UNIX is a full implementation of the Sun MicrosystemsTM Java 2 Platform - the technology and environment described in the SunTM specifications of the Java 2 Platform, Standard Edition, v. 1.3.0_02. (The _02 suffix indicates the patch level of the Sun J2SE that J2SE 1.3 for Caldera UNIX corresponds to.)
This product was previously known as the
Java 2 Standard Edition for SCO Operating Systems.
In May 2001, the operating systems business of SCO, Inc.,
was acquired by and made part of Caldera International, Inc.
These Release Notes refer to this product as being for
"Caldera UNIX Operating Systems"
to distinguish the
operating systems supported by this Java implementation
from the existing Caldera OpenLinux® operating system.
There is a
separate Java 2 Standard Edition
implementation available for Caldera OpenLinux.
| Software: |
Supported Caldera UNIX platforms:
|
| RAM: | 64 MB |
| Disk Space: | Minimum 40 MB |
J2SE 1.3 for Caldera UNIX is NOT available for the SCO UnixWare® 2 operating system.
J2SE 1.3 for Caldera UNIX is not supported on older versions of the supported operating systems, such as SCO OpenServer Release 5.0.5 or UnixWare 7 Release 7.1.0.
J2SE 1.3 for Caldera UNIX cannot be used with the older OSRcompat packages that were released together with UnixWare 7 Release 7.0, UnixWare 7 Release 7.1.0, or UnixWare 7 Release 7.1.1.
For the most part the J2SE 1.3 is identical for all supported platforms, and everything in these release notes applies to all supported platforms unless otherwise noted.
[*] Package urwfonts is available as
part of the Open UNIX 8 media kit and is automatically installed as part
of Initial System Load.
Package freefonts is available as part of
"Caldera Open Source Software with Skunkware", formerly known as the
SCO Open License Software Supplement or as
SCO SkunkwareTM.
It is available for free download
from
http://www.sco.com/skunkware/
or on Skunkware CD-ROMs in the media kits for SCO OpenServer 5 or UnixWare 7,
or in the Caldera Open Source Software with Skunkware OU8 CD-ROM in the
media kit for Open UNIX 8.
Package urwfonts is the (URW)++ subset of
package freefonts.
[**] Package set udkrtfs,
is available for free download
from
http://www.sco.com/download/. Click on "UNIX", then
choose "UnixWare and OpenServer Development Kit Feature Supplement 7.1.1b",
then look for the downloadable file udkrtfs.image.Z.
This set also includes package OSRcompat version 7.1.1b.
(Which packages the set installs will depend upon which operating system
you are on.)
[***] These are Support Level Supplements (SLS) that are provided to Caldera UNIX customers to fix problems reported in our products. These are available for free download via anonymous ftp from ftp://ftp.sco.com/pub/openunix8, ftp://ftp.sco.com/pub/unixware7, and ftp://ftp.sco.com/pub/openserver5.
Individual supplements (also known as "ptfs") are routinely bundled into larger Maintenance Supplements. These ptfs are then considered obsolete (or superseded) and removed from the download site. Any superseded ptfs that have been replaced by a maintenance supplement, will be listed and described in the maintenance supplement documentation. Be sure to check the Caldera Support page at http://www.sco.com/support/ftplists for the latest listings of all supplements that are available for each of Caldera's products.
However, an issue arises if
UnixWare 7 NonStop® Clusters Release 7.1.1+IP (NSC 7.1.1+IP)
is installed. This has the same requirements as are listed
for UnixWare 7 Release 7.1.1. Installing the urwfonts or
freefonts and udkrtfs packages on an
NSC 7.1.1+IP system is not a problem. However you cannot generally
install UnixWare 7 Release 7.1.1 ptfs on an NSC 7.1.1+IP system.
Instead, package nsc1011x is installed, which
bundles a number of UnixWare 7 Release 7.1.1 ptfs together in a form
suitable for use on an NSC 7.1.1+IP system.
As of this writing, the current version of this package
nsc1011g does not include the
ptf7410h and libsocket supplement (previously ptf7631e) levels required by
J2SE 1.3 for Caldera UNIX. To compensate for this, the java2sdk3
and java2jre3 packages do not check for the presence
of these ptfs. However, libthread, which is the subject
of ptf7410h, does not have any NSC 7.1.1+IP dependencies,
and so you can update it by hand from a UnixWare 7 Release 7.1.1 system
where ptf7410h is installed. But this cannot be done for
libsocket, the subject of ptf7631e, because
it does have NSC 7.1.1+IP dependencies. The consequence of not
having the ptf7631e fix installed is that the
jdb debugging tool may not operate properly.
J2SE 1.3 for Caldera UNIX includes improvements in performance, functionality, and reliability over the previous Java releases from SCO, Java 2 Software Development Kit, Standard Edition, version 1.2.2-001 and Java Development KitTM 1.1.8.
For a complete list of new Sun features in Java 2 Standard Edition version 1.3, visit http://java.sun.com/j2se/1.3/docs/relnotes/features.html. (Potential compatibility problems between this release and J2SDK 1.2.2 and earlier Java releases are described at http://java.sun.com/j2se/1.3/compatibility.html.)
The following changes specific to the Caldera UNIX implementation have been made, relative to JDK 1.1.8 for SCO (the most recent Java for SCO release prior to this one):
MAP_NORESERVE support being added
to the operating system
Relative to J2SDK 1.2.2 for SCO, these additional changes have been made:
/usr/java in addition to
/usr/java2
urwfonts or freefonts may
be used to supply the fonts needed by Java
Finally, this release contains fixes for a number of SCO-specific problems found in prior releases.
Note that there was an earlier release of J2SE 1.3.0_02 for Caldera UNIX
before this one. It was documented as a final release for Open UNIX 8 and
UnixWare 7, but as only a beta release for SCO OpenServer 5.
Its build version string, as shown by the
java -version command, was
*FCS-OU8*FCS-UW7*BETA-OSR5*:010602-10:46.
This newer release is a final release for SCO OpenServer 5, and also contains
fixes for Caldera-specific problems on Open UNIX 8 and UnixWare 7
discovered since the earlier release went out.
This newer release has a build version string of
*fixes-OU8*fixes-UW7*FCS-OSR5*:<later-date-and-time>.
| Approx. Size | ||
java2sdk3 | 36 MB |
Runtime Support:
java, the Java virtual machine (JVM);
the JIT compiler;
appletviewer, the Java Applet Viewer;
Java Foundation Classes (JFC) & Swing Package; and
basic API libraries:
language support,
I/O,
AWT,
networking,
utilities,
images,
media,
math,
compression,
and
security.
Development Tools:
Distributed applications and database access:
|
java2pls3 | 39 MB |
Java 2 demo applets and applications;
Demos of Swing set functionality;
native method demos;
Debuggable versions (_g-suffixed)
of many of the commands and libraries.
|
java2jre3 | 25 MB |
Java Runtime Environment (see following section)
|
java2jre3.
This package matches the Sun product configuration of the Java Runtime Environment (JRE). The JRE 1.3 for Caldera UNIX is the minimum standard Java platform for running Java programs. It contains the Java virtual machine, JIT compiler, Java core classes and supporting files, and Java application launcher. The JRE does not contain any of the development tools (such as appletviewer or javac) or classes that pertain only to a development environment. For such tools, use the J2SDK 1.3 for Caldera UNIX.
One particular purpose of the JRE package is so that licensed independent software vendors (ISVs) can bundle it with their Java application, if desired. That way, the application and the Java version it has been tested on can be installed together on customer machines, rather than relying on whatever Java version is currently installed on those machines.
The java2jre3 package is by default installed in
/usr/jre2/, with that actually being a symbolic link
to /opt/jre2-1.3/.
Unlike the java2sdk3 and java2pls3
packages, however, it is possible
for an ISV or system administrator to change where the JRE is installed.
ISVs wanting to do this would change the value of BASEDIR
in the pkginfo file and then repackage the java2jre3
package. The JRE would then install into
BASEDIR/opt/jre2-1.3/.
System administrators wanting to do this
would change the value of basedir
in the /var/sadm/install/admin/default file, and then
the JRE would install into basedir/opt/jre2-1.3/.
Or, they could copy /var/sadm/install/admin/default somewhere
else, modify the value of basedir there, and then tell
pkgadd to use that alternate file with the -a
option. Finally, if basedir=ask is set in that file, then the
pkgadd command will prompt the installer for the desired
package base directory.
First you must obtain and install any necessary prerequisite packages, as explained in System Requirements and Supported Platforms.
When those installations are complete, install the core Java 2 SDK
(package name java2sdk3):
# pkgadd -d /mnt java2sdk3
Then you can install the Java 2 SDK additional materials, if desired
(package name java2pls3):
# pkgadd -d /mnt java2pls3
First you must obtain and install any necessary prerequisite packages, as explained in System Requirements and Supported Platforms.
When those installations are complete, install the core Java 2 SDK
(package name java2sdk3):
# pkgadd -d /mnt java2sdk3
Then you can install the Java 2 SDK additional materials, if desired
(package name java2pls3):
# pkgadd -d /mnt java2pls3
java2sdk3 package is installed automatically
during Initial System Load (ISL) of the Open UNIX 8 Release 8.0.0 Base OS.
(The java2sdk3 package is on one of the Base OS CDs).
The prerequisite urwfonts package is also installed
automatically during this time.
However, if you de-selected the java2sdk3 during ISL,
you can install it from the Open UNIX Development Kit CD in the following way:
Mount the CD-ROM and install the Java 2 SDK
(package name java2sdk3):
If your machine has more than one CD-ROM drive, specify the CD-ROM device exactly (e.g.# mount -F cdfs -r /dev/cdrom/* /mnt # pkgadd -d /mnt urwfonts # pkgadd -d /mnt java2sdk3
/dev/cdrom/c0b0t6l0).
Similarly for the other package:
# pkgadd -d /mnt java2pls3
While the J2SE is accessed through the /usr/java2 pathname,
installation actually places its contents into /opt/java2-1.3/.
Then a symbolic link is made from /usr/java2 to
/opt/java2-1.3/.
You can have multiple versions of Java installed on your system at the same time. Installation of J2SE 1.3 will not automatically remove any previous versions of Java from your system.
If you already have J2SDK 1.2.2 for SCO on your system, all that installation
of J2SE 1.3 will do is change the /usr/java2 symbolic link from
/opt/java2-1.2.2 (the actual installation point of J2SDK 1.2.2)
to /opt/java2-1.3/. You may still access J2SDK 1.2.2 directly
by naming its actual installation point. For example, the command
/opt/java2-1.2.2/bin/java will start up the J2SDK 1.2.2
virtual machine.
If you do not already have JDKTM 1.1.8 for SCO,
or an earlier version of JDK 1.1.x
for SCO, on your system, then installation of J2SE 1.3 for Caldera UNIX
will also create
/usr/java as a symbolic link to /opt/java2-1.3/
in addition to /usr/java2. Thus, you can access the
J2SE 1.3 for Caldera UNIX virtual machine by either
/usr/java/bin/java or /usr/java2/bin/java,
and similarly for other Java commands.
Being able to use /usr/java has several advantages:
It is the place where Java is accessed on many other systems,
including on Caldera OpenLinux, and thus is often the place third-party
scripts will look for Java. It is the place where Java
first-class executable support on Open UNIX 8 will
look for Java. And it is the place that is by default added to your
PATH environment variable when login accounts are created
on UnixWare 7 or Open UNIX 8.
However, if you do
already have a JDK 1.1.8 or earlier 1.1.x for SCO version installed
on your system, then you may not want the /usr/java symbolic
link changed to point to J2SE 1.3 for Caldera UNIX. For example, you may have
applications that do not run correctly under Java 2, whose scripts are
expecting Java 1.1.x to be in /usr/java.
In this case, the install will notify you of the potential conflict,
and give you a choice of whether you want /usr/java to
be changed to point to J2SE 1.3 for Caldera UNIX
or whether you want it left alone.
The only exception to this is if you are upgrading your system from UnixWare 7 Release 7.1.1 to Open UNIX 8 Release 8.0.0; the update is non-interactive and thus will always change the symbolic link. You can manually restore the symbolic link afterwards if you so desire.
Note however that even if /usr/java is changed,
the actual installation point of /opt/jdk-1.1.x of any
JDK 1.1.x for SCO will be unchanged, and you can access its commands by
using a full pathname. For example
/opt/jdk-1.1.8/bin/java will start up the JDK 1.1.8 for
SCO virtual machine.
Similar considerations apply to the JRE 1.3 for Caldera UNIX and previous JRE versions.
Instead, you may browse Sun's complete documentation for Java 2 SDK, Standard Edition Version 1.3 at http://java.sun.com/j2se/1.3/docs/index.html. This contains the very latest and most accurate documentation for J2SE 1.3.
The Japanese version of the documentation may be found at http://java.sun.com/j2se/1.3/ja/docs/ja/index.html.
Both the English and Japanese versions of the documentation may be downloaded as a large HTML bundle at http://java.sun.com/j2se/1.3/docs.html.
Where the documentation differs depending upon the underlying operating system (such as with the SDK tool documentation), follow the "SolarisTM" version (not the "LinuxTM" or "Win32" versions).
Note that there are also useful
Sun and Caldera UNIX demonstration uses of
J2SE 1.3 and J2SDK 1.3 at /usr/java2/demo/ when
the java2pls3 package has been installed.
After the Java 2 SE packages are installed, we recommend that you
set PATH in your .profile startup file
(or whatever startup file is used in your shell)
to include
the directory where the Java 2 commands are installed,
/usr/java2/bin or /usr/java/bin (if J2SE 1.3
for Caldera UNIX
has been installed there as well). In the later case, modifying
your startup file may not be necessary, as UnixWare 7 and Open UNIX 8
login accounts are usually created with /usr/java/bin
as part of the PATH.
Caldera has provided a functional extension to the Sun Java 2 SE for use on the Open UNIX 8 platform: Java classes as first-class executables. This extension does not affect the Java 2 APIs; it just affects how Java can be invoked.
When javac is used to compile one or more classes, it
will set the execute permissions bit on for the .class
file if the class contains a main method. (This happens
on all Caldera UNIX platforms.)
Then, on Open UNIX 8 only, you can execute a Java application simply by giving the name of the main class:
Open UNIX 8 will look for$ foo.class
foo.class by use of the
PATH environment variable, just as it would for
any other executable. foo.class must also be
in the CLASSPATH, as in normal execution.
(This extension also exists on the UnixWare 7 platform, but it
will attempt to invoke JDK 1.1.x for SCO, not J2SE 1.3 for Caldera UNIX.
As a work-around, if you copy the file /usr/bin/javaexec
from an Open UNIX 8 system to a UnixWare 7 system, then J2SE 1.3 for
Caldera UNIX will be invoked.)
Furthermore, by making a hard link or symbolic link such as
you will be able to execute the application simply by saying$ ln -s foo.class foo
This gives you the ability let users invoke utilities without knowing the utilities are written in Java. For this to work you must keep the name prefix intact and the class file intact. That is, you have to keep$ foo
foo.class
somewhere, and then you can make a hard or soft link
of foo to it. foo can be in another directory,
but you can't change
the name; i.e., you can't link bar to it. That's because once the
system invokes the JVM, it expects to find a foo.class file there.
For this same reason you also can't just rename foo.class to
foo, because the JVM will still need a foo.class.
(You could copy foo.class to foo,
but that will of course waste disk space compared to a link.)
Of course, you can always use the traditional way of executing a Java application:
In this case,$ java foo
java must be in the PATH,
and foo.class must be in the CLASSPATH.
A just-in-time (JIT) compiler improves Java performance by, as the program is executing (hence the name), compiling Java method bytecode to native Intel® IA-32 machine code. On subsequent executions of the method the machine code is executed instead of the bytecode being re-interpreted. Thus, a JIT compiler is a run-time component, not a development component (as conventional language compilers are).
A JIT compiler is part of the base J2SE 1.3 for Caldera UNIX product
and package java2sdk3 (or java2jre3 if the
JRE package is being used).
It is a transparent component:
it is always there and is always executing unless it is explicitly
turned off by the user.
It does not have to be separately licensed or installed.
You do not have read or use any of the information in the rest of this section in order to gain the benefit of the JIT; the information is here only for those wanting a better understanding of what the JIT does, or for those wanting to exercise further control over the JIT.
The JIT compiler in J2SE 1.3 for Caldera UNIX
is named sunwjit and is based upon the JIT
compiler of the same name from Sun, but it has
been significantly enhanced by Caldera.
The JIT compiler in J2SE 1.3 for Caldera UNIX has the ability to compile or inline every method in the program, the first time the method is invoked (except for a few primordial methods which cannot be compiled until the JIT compiler itself is loaded), although it may choose to defer compilation for a given method. Methods of dynamically loaded classes may be compiled after the class is loaded. Class initializers are never compiled. If for some reason a method cannot be compiled (such as an internal error in the JIT, or invalid bytecode contents), it is interpreted. Jitted code is not saved across sessions of the JVM.
How much the JIT improves performance depends greatly upon the nature of the application being run. Applications that are compute-intensive benefit the most, while those that are dominated by object creation/garbage collection, graphics, or networking tend to benefit less. The only way to know the benefit for your application is to measure it.
The JIT compiler runs by default.
It can be explicitly requested via its sunwjit name, but this
is not necessary.
Normally there is no reason to suppress running of the JIT, but you might want to do it in the following situations:
JAVA_COMPILER
environment variable to the empty value, or by setting the
java.compiler property to the empty value. Examples:
$ java hello # JIT will run $ JAVA_COMPILER=sunwjit java hello # JIT will run $ java -Djava.compiler=sunwjit hello # JIT will run $ JAVA_COMPILER= java hello # JIT will not run $ java -Djava.compiler= hello # JIT will not run
The environment variable JIT_ARGS provides further control
over execution of the JIT. You can define JIT_ARGS as a
string containing one or more of these space-separated options:
traceshow which methods are compiled or inlined compile(method-list)compile just these methods exclude(method-list)do not compile just these methods dump(method-list)dump the generated assembly code for these methods bco=on|offalways run/don't run the bytecode optimizer part of the JIT
The method-list is a comma-separated list of method names, possibly qualified by class names. The class name part is separated by slashes. If only a class name is given, all methods of that class are selected. If no method-list is given, the option applies to all methods. Examples:
In particular,$ JIT_ARGS=trace java hello # show what the JIT does $ JIT_ARGS="dump(hello)" java hello # show how the JIT does it (lots of output!) $ JIT_ARGS="trace compile(myclass.)" java myclass # only jit myclass's methods $ JIT_ARGS="trace exclude(java/lang/System.exit)" java myclass # jit everything except java.lang.System.exit()
JIT_ARGS=trace is useful in verifying that the
JIT is installed correctly and is actually executing.
The bytecode optimizer is a particular part of the JIT, which by default only
runs when a method is being jitted during the first time it is called (for
internal reasons this optimizer is usually ineffective when used for a method
for which compilation has been deferred). The bco= option may
be used to force the bytecode optimizer to either always or never run when
a method is compiled, which may be useful for
pinpointing the source of performance problems or other JIT problems.
All JIT compilers come with a trade-off: the cost of the time it takes to pause execution of a method and do the compilation to machine code (once per method per program) versus the benefit of the time saved by subsequent invocations of that method running as machine code rather than being interpreted. For example, for a short method that is only called once, this trade-off is obviously a loss, while for a long method called many times, this trade-off is clearly a win.
By default, the JIT compiler in J2SE 1.3 for Caldera UNIX attempts to maximize this trade-off for each individual method, by using two heuristics. One is the size of the method in bytecodes: it is assumed that shorter methods take less time to compile and less time to execute (although measurements have shown that the correlation is rather weak for the latter, especially for smaller-sized methods). The other is the number of times the method has already executed during the program's run: it is posited that those methods that have already been called a lot, will be the ones that will tend to be called a lot for the rest of the program's lifetime.
(This is a Caldera enhancement; in the base Sun version of sunwjit,
methods are always compiled the first time they are called.)
Two environment variables are used to control these heuristics:
JIT_MIN_TIMES and JIT_MIN_SIZE, both of which
can be set to non-negative integer values.
JIT_MIN_TIMES=n
tells the JIT to compile a method after it has been executed n
many times, no matter what the size of the method.
JIT_MIN_SIZE=m
tells the JIT to compile a method that is greater than or equal to
m bytes in bytecode size, no matter how many times it has been
executed.
The default values used by the JIT are JIT_MIN_TIMES=40
and JIT_MIN_SIZE=150; you do not need to set these environment
variables unless you want to change these values for your application.
In between the points given by these limits, the JIT interpolates the heuristic; so, for example, a method of 75 bytes in size might be compiled once it has executed 30 times.
Example of the use of these environment variables might be:
$ JIT_MIN_TIMES=0 java my_app # methods will be jitted after 0th time called $ JIT_MIN_TIMES=100 JIT_MIN_SIZE=500 java my_app # only jit the really "heavy hitters"
(The first example above reproduces the default behavior in previous releases of Java for SCO platforms, where every method was compiled the first time it was called.)
This heuristics strategy significantly increases the performance of
some short- or medium-lived
applications, such as the javac Java language translator.
Even for long-lived applications, this strategy often improve the start-up time of the application, especially when Swing or AWT is involved, with no subsequent performance degradation compared to the older strategy of always jitting methods the first time they are seen.
However, for some long-lived applications where the start-up time is not of
importance, it might be better to set JIT_MIN_TIMES=0 to compile
everything the first time it is called. This also has the benefit of
running the bytecode optimizer part of the JIT for every method, which
will result in the best generated code being produced. In running long-lived
server-oriented benchmarks, however, the default settings have proved
best over the life of the program.
In conclusion, the only way to find out for sure whether adjusting any of these JIT-related environment variables will benefit your application is to experiment with it, using different values.
"Green threads" refers to a model in which the Java virtual machine itself creates, manages, and context switches all Java threads within one operating system process. No operating system threads library is used.
"Native threads" refers to a in which the Java virtual machine creates and
manages Java threads using the operating system threads library - named
libthread
on UnixWare 7 and Open UNIX 8 - and each Java thread is mapped to
one threads library thread.
J2SE 1.3 for Caldera UNIX supports both models (except on SCO OpenServer Release 5), and it is up to you to decide which to use for your application. Native threads is the default on UnixWare 7 and Open UNIX 8 (this is a change from previous releases of Java on UnixWare 7, when green threads was the default), while only green threads is available on SCO OpenServer Release 5.
To specify the threads model, set the THREADS_FLAG
environment variable to either green or native.
For convenience, the java command also has an option,
-green or -native, that can be used if it
is the first option specified; but for
other commands, the environment variable must be used. Some examples:
$ java my_app # native threads will be used $ THREADS_FLAG=green java my_app # green threads will be used $ THREADS_FLAG=native java my_app # native threads will be used $ java -green my_app # green threads will be used $ THREADS_FLAG=green appletviewer my_applet.html # only way to set green threads
One reason to use green threads had been that it was the more mature implementation, but by now this is no longer true.
Another reason to use it is that switching the threads model may change the behavior of the Java application. The Java language specification does not give a lot of precise details about how Java threads are scheduled, so there is some room for implementation dependencies in this area (unlike the rest of the Java specification). Java applications that (incorrectly) make assumptions about how threads will be scheduled may work under one threads model but not under the other. Older Java applications were written under green threads (that was the first model available on most platforms, including SCO), and for them the chances are that the native threads model would be more likely to expose incorrect application dependencies. However, in recent years many system vendors have been providing Java implementations that only implement native threads, or that default to native threads, and so newer Java applications are less likely to have these dependencies.
Finally, on a uniprocessor machine, green threads sometimes has performance advantages over native threads, although the difference tends to be relatively minor.
There are two major potential advantages to using native threads, in addition to it intuitively being the "right way" to implement Java threads - it uses the threads capability of the underlying operating system.
The first advantage is performance on multiprocessor (MP) machines. In green threads all Java threads execute within one operating system lightweight process (LWP), and thus UnixWare 7 or Open UNIX 8 have no ability to distribute the execution of Java threads among the extra processors in an MP machine. But in the native threads model, each Java thread is mapped to a UnixWare 7 or Open UNIX 8 threads library multiplexed thread, and the threads library will indeed map those threads to different LWPs as they are available.
The performance benefit from using native threads on an MP machine can be dramatic. For example, using an artificial benchmark where Java threads are doing processing independent of each other, there can be a three-fold overall speed improvement on a 4-CPU MP machine.
The second major advantage of native threads is when native methods are being used. In order for the green threads implementation to perform non-blocking I/O, a number of system calls are "wrapped" by the JVM to use green threads synchronization primitives and the like. If native methods make system calls in some way that the green threads JVM doesn't expect, these wrappers often cause severe problems. As a consequence, there are a number of restrictions placed upon native methods in green threads mode, as listed in the section Native Methods below.
In comparison, in native threads mode
there is no need for I/O system call wrappers, and
there are no restrictions upon what native methods may do, as long as
they are coded to be thread-safe and are built with -Kthread.
A final advantage of native threads is that it usually gives a clearer picture of a program's activities when debugging at the native methods level with a debugger.
By default, scheduling in green threads mode is not pre-emptive.
This means that if one thread has control of the processor and is
not giving it up (by doing an I/O operation or making a
Thread.yield call), other higher- or equal-priority
threads may never get a chance to run.
This behavior can be changed by using Sun's formerly-documented green threads
time slicing option -Xtsnn. This will force
the JVM green threads scheduler to interrupt threads every nn
milliseconds and give control to other threads that eligible to run.
For example, this command:
will force time slicing every 10 milliseconds.$ THREADS_FLAG=green java -Xts10 my_app
When using multiplexed threads in the UnixWare 7 or Open UNIX 8 threads library,
as the Java virtual machine does in native threads mode, the key to
how much real concurrency is achieved is how many LWPs are active
within the process. J2SE for Caldera UNIX uses the threads library's
thr_setconcurrency() interface to guide this, and
there are three different schemes for controlling the number of LWPs.
By default,
the number of LWPs
is set dynamically as the Java
application executes. The base level is one LWP for each processor
in the machine.
Then, additional LWPs are requested as threads are
blocked in certain system calls, these being
recv accept send waitid read poll, all of which tend to
block their threads for a long time within the JVM. The request level
is decremented once these calls return. This default behavior
is a reasonable heuristic that on the one hand tries to maximize useful
concurrency and reduce scheduling
stress on the threads library, but on the other
hand tries to conserve a dear system resource.
For compatibility with some previous Java for SCO releases,
this scheme is also used if the THR_INCR_CONC environment variable is set to nothing or to the empty string.
Alternatively,
if the THR_INCR_CONC environment variable is set to zero:
the number of LWPs created by the JVM is specified to be equal to the number of active processors in the machine. This is the minimum allocation that will take advantage of real parallelism in multiprocessor machines. (This was previously the default in some Java for SCO releases.)$ THR_INCR_CONC=0 java my_app
Finally, you can specify your own concurrency level, by setting
the THR_INCR_CONC environment variable to a positive integer.
An example would be:
In both of these alternatives, the specified number of LWPs will be requested at the beginning of execution, and the requested level will be fixed for the rest of execution; in particular, the level will not vary based on threads blocking in system calls.$ THR_INCR_CONC=20 java my_app
C and C++ native methods must be compiled and linked with the UnixWare and OpenServer Development Kit (UDK) from Caldera, version 7.1.1 or later (unless the JNI Invocation API is being used, in which case the version 7.1.1b Feature Supplement or later is required), or with the Open UNIX Development Kit (OUDK).
This means that native methods cannot be built with the SCO OpenServer Release 5 Development System.
Some of the reasons for this requirement include:
long long data type,
to match the Java 64-bit long data type
libC.so) rather than an archive (libC.a)
Another important limitation with native methods is upon the kinds of system operations that a native method can do when "green threads" is being used as the Java threads implementation model (see the Threads: Green or Native section above). Under green threads the following restrictions are in place:
libthread
threads library from
UnixWare 7 or Open UNIX 8.
write, writev, read, readv,
getmsg, putmsg, poll, open, close, pipe, fcntl,
dup, creat, accept, recv, send, recvfrom, sendto, socket,
connect, select, ioctl (including their UnixWare 7 or Open UNIX 8
versioned names with _x prefixes) -
you may run into trouble because of green threads wrappers.
However it is safe to make these system calls
from JNI Invocation C or C++ code before
the Java virtual machine is started
up, because at that point the green threads wrappers are not yet activated.
None of these limitations exist with the "native threads" implementation model, so if you are coding native methods and that model is available to you, it is strongly recommended that you use it.
Caldera UNIX-specific
examples of the commands needed to build old- and new-style
native methods with C and C++ are
included in the demos part of the J2SDK 1.3 for Caldera UNIX distribution
(when java2pls3 package is installed), in the directory
/usr/java2/demo/native,under the subdirectories
native_c_demo
jni_c_demo
native_c++_demo
jni_c++_demo
jni_invoc_demo.
mk script to run the example.
It is highly recommended that
you follow the command invocations given in all these examples, for unless
the native code is built correctly, it will not work as intended.
Another compiler system that can be used for building native methods is the GNU GCC compiler, described in general at http://gcc.gnu.org.
If native method or JNI invocation code is written in C, the GNU gcc compiler that generates code for the UDK/OUDK environment may be used.
On Open UNIX 8, this is the GNUgcc package within the
open source OSTools product set
that Caldera builds and ships
as part of the OUDK CD-ROM.
This same package may also be installed on UnixWare 7.
Alternatively on UnixWare 7, the Skunkware gcc from
http://www.sco.com/skunkware/ may be used.
On SCO OpenServer Release 5, the regular
gcc for OpenServer
cannot be
used; instead, you must build the
OpenServer-hosted, UDK-targeted gcc described at
http://gcc.gnu.org/install/specific.html#ix86-*-udk.
If native method code code is written in C++, the GNU g++
compiler that generates code for the UDK/OUDK environment may be used, with
the same guidelines as for C. Note that g++ version 2.95.3 or higher
(as is found in package GNUgcc within OSTools)
must be used, since the previous g++ version 2.95.2 had several
problems building C++ code with the
-shared option, which made it very difficult to use for Java
native methods.
If JNI invocation code is written in C++, the
GNU g++ compiler can only be used if the C++ program is very simple and
does not use many C++ language or library features.
This is because part of the JDK itself is
built with the UDK/OUDK C++ compiler, and in the JNI invocation context,
the UDK/OUDK and GNU
C++ runtime systems usually cannot coexist together. (This problem does not
occur in the native method context because there
the C++ runtime usages are isolated
to dlopen'd native code libraries that do not have any
visibility to each other. This is not the case in JNI invocation
where the JVM is visibly linked against the C or C++ main program.)
The /usr/java2/demo/native directories described above
may also be used to run native methods examples with the GNU compilers.
Pass the option gcc or g++ into the
mk scripts.
All three examples in the jni_invoc_demo
directory will run under gcc, but only the hello example
will run under g++.
Debugging of Java applications is done with the J2SDK-provided
jdb debugger, as described in the relevant Sun
documentation.
Debugging of C or C++ native methods, however, must be done with the UDK or OUDK debugger; this section describes how to go about this. This discussion is also applicable to isolating or troubleshooting potential problems within the JVM itself, since the lower layers of the JVM are in effect C native methods.
Core dumps should never occur within Java. If they do, then either there
is an application bug in a native method, or there is an internal bug
within the JVM, or there is an internal bug within a Caldera UNIX operating
system library. Java core dumps tend to be large; you may need to
set ulimit -c unlimited to avoid having the core file
be truncated (typically to 16 MB) and thus be unreadable by the UDK/OUDK
debugger.
Core dumps from the JVM will usually have a few levels of signal handlers on the stack subsequent to the actual point of failure. This is true in both green threads and native threads modes. An example would be:
kauai: debug -c core.22890 /usr/java2/bin/x86at/green_threads/java_g
Core image of java_g (process p1) created
CORE FILE [_kill]
Signal: sigabrt
0xbffa45b3 (_kill+12:) jb +0x5ce [ _cerror ]
debug> stack
Stack Trace for p1, Program java_g
*[0] _kill(0x596a, 0x6) [0xbffa45b3]
[1] abort(presumed: 0xbff69ea0, 0x8046d74, 0x8046d74) [0xbffd835a]
[2] Abort(presumed: 0xbff84458, 0x8055e7c, 0x804c378) [../../../../src/share/javavm/runtime/interpreter.c@1441]
[3] panicHandler(sig=8, siginfo=0x8047018, uc=0x8046e18) [../../../../src/unixware/javavm/runtime/signals_md.c@324]
[4] userSignalHandler(sig=8, info=0x8047018, uc=0x8046e18, arg=0xbff58de0) [../../../../../src/unixware/hpi/src/interrupt.c@120]
[5] intrDispatch(interrupt=8, siginfo=0x8047018, context=0x8046e18) [../../../../../src/unixware/hpi/src/interrupt.c@106]
[6] intrDispatchMD(sig=8, info=0x8047018, uc=0x8046e18) [../../../../../src/unixware/hpi/green_threads/src/interrupt_md.c@131]
[7] _sigacthandler(presumed: 0x8, 0x8047018, 0x8046e18) [0xbffb5fd1]
[8] Java_nfib_fib(env=0x804c2fc, cls=0x8047118, n=2) [fib.c@13]
[9] args_done() [0xbff59a05]
debug>
The actual point of failure is at frame level [8] in this case. Note also
that when the JIT is in use, you don't see the rest of the stack;
it usually ends as shown, or in a
function named something like JIT_CALLBACK1_MARKER. If you
turn off the JIT, then you can see it, but it will just be a bunch of
internal routines inside the JVM (with names like do_execute_java_method
) that won't tell you much. In other words, there is no debugging
tool available that will show you both the Java stack and the native
methods stack at the same time.
However, when using native threads,
you can make use of the JVM's Java thread dumps for this purpose.
These are what you see
when a Java process aborts;
you can also get one by doing ^\ (control-backslash) at the
command line as a Java application is running (this is especially useful
if a JVM process is hung, frozen, or looping) or equivalently by sending a
SIGQUIT signal to the process, such as with the
kill -3 command. (You can also get some
of the same information by grabbing with or running under jdb.)
You'll see entries in the Java threads dump like
"Thread-464" (TID:0xbf0a1cc8, sys_thread_t:0x8472010, state:R, thread_t: t@4
66, sp:0xbaee3498 threadID:0x0, stack_base:0xbaee3c64, stack_size:0x20000) prio=
5
java.io.PrintStream.println(Compiled Code)
T.run(Compiled Code)
ps
command, the number in the "Thread" column is the same as this
thread number. (This is different from the "ID" column, which has the
p1.nn identification used in debugger commands,
but you can use the ps
output to correlate the two.)
In some cases, an abort() call can completely obscure the
actual place of failure, especially if the JVM runs into further trouble while
trying to print the Java thread dumps. In this case, when using native
threads, you can define
the environment variable JVM_NOT_HANDLE_SIGABRT; this will
cause an immediate core dump and exit from the point of the abort,
without the JVM getting involved. Then bringing up the debugger on the
core file and doing a stack trace on the current thread will show you
to the exact location of failure.
Java threads dump can also be produced when using green threads, but there
is no good way to associate the Java thread stacks with native method
thread stacks, since the latter are not visible to the debugger.
The JVM_NOT_HANDLE_SIGABRT environment variable has no
effect in green threads.
Of course, to do real native methods debugging you'll want to
run the JVM from within the debugger. To do this you'll need to invoke
the JVM executable directly. First, you should use the java_g
version of the JVM, since that contains debugging information. Second,
if you look at /usr/java2/bin/java_g, you'll see that it's
a link to a script called .java_wrapper in that same
directory, that sets up and exports
the LD_LIBRARY_PATH and _JVM_THREADS_TYPE environment
variables before calling the actual JVM executable in
/usr/java2/bin/x86at/green_threads/java_g.
(Note that unlike in JDK 1.1.x, the wrapper script does not set the
CLASSPATH environment variable.)
If you invoke /usr/java2/bin/java_g through ksh -x
you'll see the values LD_LIBRARY_PATH and _JVM_THREADS_TYPE
are set to; you can set those manually at the command line (store in
a script that you "dot" if you debug frequently), then invoke the debugger:
$ . setup_java # your script to set LD_LIBRARY_PATH and _JVM_THREADS_TYPE $ debug -ic # or can use graphical version debug> create /usr/java2/bin/x86at/native_threads/java_g my_app debug> run debug>
Another complication sets in when you want to use symbols (to set breakpoints
on, for instance) that are outside of the JVM, such as in native methods.
The dynamic libraries that contain native methods are loaded by the JVM
via a dlopen() call, and until this happens, symbols in
the native methods won't be visible to the debugger.
The solution to this is to set a breakpoint inside the JVM at the point
where the dynamic library has been loaded, but before code in the libraries
is called. For J2SDK 1.3 for Caldera UNIX the appropriate breakpoint is
linker_md.c@143. You then have to stop the JVM there as
many times as necessary until the library you are interested in has
been loaded.
Here is an example demonstrating both the problem and the solution:
You can debug normally from that point on. (How many times to stop it depends upon how many J2SDK native libraries are loaded, which depends upon what your application is doing. The above shows the correct number for a command-line application with the JIT compiler running.)$ debug -ic debug> create /usr/java2/bin/x86at/green_threads/java_g nfib New program java_g (process p1) created HALTED p1 [main in ../../../../../src/share/bin/java.c] 81:debug> stop Java_nfib_fib Error: No entry "Java_nfib_fib" exists debug> stop linker_md.c@143 EVENT [1] assigned debug> r STOP EVENT TRIGGERED: linker_md.c@143 in p1 [sysLoadLibrary in ../../../../../src/unixware/hpi/src/linker_md.c] 123: debug> r STOP EVENT TRIGGERED: linker_md.c@143 in p1 [sysLoadLibrary in ../../../../../src/unixware/hpi/src/linker_md.c] 123: debug> r STOP EVENT TRIGGERED: linker_md.c@143 in p1 [sysLoadLibrary in ../../../../../src/unixware/hpi/src/linker_md.c] 123: debug> stop Java_nfib_fib Error: No entry "Java_nfib_fib" exists debug> r STOP EVENT TRIGGERED: linker_md.c@143 in p1 [sysLoadLibrary in ../../../../../src/unixware/hpi/src/linker_md.c] 123: debug> stop Java_nfib_fib EVENT [2] assigned debug> run STOP EVENT TRIGGERED: Java_nfib_fib in p1 [Java_nfib_fib in fib.c] 8: if (n == 12) debug>
If you do a lot of this kind of debugging it can be useful to set up
an alias in your ~/.debugrc file, which
allows you to define a whole series
of convenience commands to set up a typical native methods debugging session.
An example of a full .debugrc alias for JVM green threads
debugging might be look something like:
alias cj13 set $LD_LIBRARY_PATH=".:/usr/java2/bin/./../jre/lib/x86at/green_threads:/usr/java2/bin/./../jre/lib/x86at/classic:/usr/java2/bin/./../jre/lib/x86at:" ; export $LD_LIBRARY_PATH ; set $_JVM_THREADS_TYPE="green_threads" ; export $_JVM_THREADS_TYPE ; create -f none /usr/java2/bin/x86at/green_threads/java_g $1 $2 $3 $4 $5 $6 $7 $8 ; set %stack_bounds=no ; signal -i cld poll alrm ; set $JAVA_HOME="/usr/java2" ; export $JAVA_HOME
The setting of the _JVM_THREADS_TYPE and
LD_LIBRARY_PATH environment variables follows the discussion above.
The create -f none command tells the debugger to ignore child
processes caused by forks done within the X Window System libraries. The
stack_bounds setting avoids spurious warnings due to jitted
code being executed. The signal -i command keeps the debugger
from stopping on innocuous signals that the JVM handles. Setting
JAVA_HOME is necessary when debugging within the appletviewer.
For debugging when the JVM is using native threads, simply change the
green to native in the above paths.
Depending on what you are trying to debug, you probably want to add a
statement such as:
set %thread_change=ignore ;
On SCO OpenServer Release 5.0.6 and later, this is no problem, since as of that
release the standard UNIX APIs (such as gettimeofday())
have a resolution of one microsecond, which is adequate for the task.
However, on UnixWare 7 and Open UNIX 8
the normal resolution of UNIX APIs is typically much worse, on the
order of ten milliseconds or so, and as a result profiling data suffers
in terms of usefulness.
Better profiled timings can be obtained with J2SDK 1.3 for Caldera UNIX on UnixWare 7 Release 7.1.1 or Open UNIX 8 by doing the following:
JVM_USE_RDTSC. Ideally, it should be set to the speed
of the processor you are running on, in MHz. Thus, for example:
If the value specified for the environment variable is missing or invalid, 266 MHz is used as a default. It is not vital to get the processor speed correct, though, since most profiling data is expressed in terms of percentages.$ JVM_USE_RDTSC=400 /usr/java2/bin/java -Xrunhprof:cpu=times MyApp
System.Properties
can be queried. Here are some of the values that will be returned
by default on all
Caldera UNIX platforms:
java.home=/opt/java2-1.3/jre java.vendor=Caldera International, Inc. java.vendor.url=http://www.sco.com/ java.vendor.url.bug=http://www.sco.com/support/ java.version=1.3.0_02 java.vm.vendor=Caldera International, Inc. java.vm.version=Caldera-UNIX-J2SE-1.3.0_02:*fixes-OU8*fixes-UW7*FCS-OSR5*:[build-date-and-time] java.class.version=47.0 java.compiler=sunwjit
while here are values that are specific to SCO OpenServer Release 5.0.6:
os.arch=IA32 os.name=OpenServer os.version=5.0.6 java.vm.info=green threads, sunwjit
UnixWare 7 Release 7.1.1:
os.arch=IA32 os.name=UnixWare os.version=7.1.1 java.vm.info=native threads, sunwjit
and Open UNIX 8 Release 8.0.0:
os.arch=IA32 os.name=OpenUNIX os.version=8.0.0 java.vm.info=native threads, sunwjit
java_g uses a C language interpreter when the JIT is not on.
J2SE 1.3 for Caldera UNIX
contains an implementation of Sun's "classic VM" virtual
machine, together with a JIT compiler.
The more recent (and generally better performing)
Sun HotSpotTM
virtual machine is not available in the implementation described here.
Attempts to use the HotSpot-specific JVM options
-hotspot, -client, or -server
will result in a warning diagnostic, with the classic VM being invoked anyway.
However see the section on Java for Caldera OpenLinux and LKP for an alternative way to gain access to an implementation of the HotSpot virtual machine on some Caldera UNIX platforms.
Caldera is committed to maintaining Java application compatibility across all platforms. Caldera does not superset or subset the Java 2 APIs as defined by Sun.
Java Database Connectivity is a standard SQL database access interface for Java, providing uniform access for Java applications to a wide range of relational databases.
J2SDK 1.3 for Caldera UNIX contains the Caldera UNIX implementation of JDBC and includes the Caldera UNIX JDBC driver. The Caldera UNIX JDBC implementation was built upon the SCO, Inc. SQL-RetrieverTM product.
There is no need to separately install the Caldera UNIX JDBC implementation,
since it is part of the java2sdk3 installation.
It is necessary to separately install the SQL-Retriever
product if you are interested in using JDBC. The Caldera UNIX
JDBC implementation is included in the
/usr/java2/jre/lib directory as sqlr.jar.
To use it, include the appropriate path to this jar file in your
CLASSPATH.
The part of SCO that made SQL-Retriever is now known as Tarantella, Inc. As of April 2001, the SQL-Retriever product has been withdrawn from the market. However a license for residual contractual requirements may still be available, and in any case, if you already have it installed you can continue to use it.
The Caldera UNIX JDBC implementation included in J2SDK 1.3 is compliant with the Sun JDBC 1.2 specification. It is not compliant with the Sun JDBC 2.0 specification.
Third-party database vendors and other ISVs may also provide JDBC implementations that work with J2SE 1.3 for Caldera UNIX.
/usr/java2/jre/lib/font.properties
file of this release of J2SE 1.3 for Caldera UNIX.
Even for European languages, only a limited number of scalable fonts
is available on Caldera UNIX platforms. However, the SCO Open License Software
Supplement has a collection
of freely available X11 fonts in package
freefonts which helps alleviate this problem.
The consequences of missing fonts in Java 2 can be severe. For example,
without packages urwfonts or freefonts the
individual benchmark scores do not appear above their graph bars in
the once-commonly used CaffeineMark benchmark GUI harness. As another example,
the Java2D demo program gets spurious out of memory exceptions,
security exceptions,
and illegal argument exceptions, as well as not
displaying its fonts properly. For these reasons installation of
either the urwfonts or freefonts package
has been required for J2SE 1.3
for Caldera UNIX and JRE 1.3 for Caldera UNIX.
When a Java program requests a particular font of a particular size, Java 2 looks for scalable fonts first. If nothing could match, then Java 2 will try to find the fonts whose sizes and types are as close as possible, including trying the fixed-size fonts if their size is close enough. This, sometimes, could cause the font displayed to look not as you wanted, if no appropriate fonts could be found on the system the Java program is running on.
You may find useful information on these and other font issues from Sun at http://java.sun.com/products/jdk/1.2/docs/guide/internat/fontprop.html.
xhost +your_machine_name command.
a.out that
does a dlopen of a libuser.so that in turn
invokes the Java virtual machine, will not work. An a.out
that is linked with -luser but not -ljava
that calls a libuser.so that in turn invokes the Java
virtual machine, will also not work. Such an a.out must
always be linked against -ljava itself. (See
/usr/java2/demo/jni_invoc_demo for the full set of system
libraries to link against.)
/tmp filesystem is completely full,
Java commands will fail with apparently mysterious errors such as
Error: can't find libjava.so. or
UX:test (java): ERROR: Argument expected. (This is due
to Korn shell behavior rather than the J2SE itself.) The solution is
to free up space in /tmp; only a little is required.
this reference) will not be NULL as it
should be. The impact of this is negligible, though, since it is
very unlikely that NMI native methods would dynamically test against this
argument to know whether they are static or not.
java -Xss option),
while when the JIT is not running, Java frames are allocated on the "Java"
thread stack (the size of which is governed by the java -Xoss
option). Since these stacks have different default sizes (128k and 400k
respectively), it is possible for an application to experience a
StackOverflowError exception when the JIT is running but
not otherwise. If this happens, adjust the native thread stack size
accordingly. Note however that "legitimate" stack overflows in Java are
rare, since most objects are allocated on the heap; stack overflows
are usually due to application bugs (recursive loops)
or Java implementation bugs.
file(1) command
does not correctly recognize Java .class files.
This is not problem with J2SE 1.3 per se, but with the two underlying
operating systems.
If you want to have file correctly identify these files,
add the following line to the /etc/magic file:
(The fields in this line must be tab-separated.) On SCO OpenServer Release 5 the0 long 0xbebafeca uxcore:999 Java Class File
file command does recognize Java .class files,
and no modification is necessary.
MulticastSocket.leaveGroup method may not
relinquish the socket's membership in the group due to some
unknown operating system or hardware related problem.
Rebooting the machine will resolve this behavior.
jdb "run" command does not result in
the program under test starting to run. In this case,
issue a "threads" command, and then a "run" command.
connect() system call and certain signals used by the
threads library. It is corrected in the upcoming
uw711pk1 and ou800pk3 maintenance packs.
LANG=fr_FR.ISO8859-1. However,
in order for J2SE 1.3 to change its default locale to the French one,
it needs for LANG=fr_FR to be set; the fr_FR.ISO8859-1
value will not work. Thus, you should do something like:
when invoking the JVM, to change the$ LANG=fr_FR /usr/java/bin/java my_app
LANG value for the JVM
(but not for any other OpenServer applications).
(This is not a problem with J2SE 1.3 per se,
but rather with the different locale setting conventions between UnixWare 7
and SCO OpenServer Release 5, and how those differences are reflected
through the OSRcompat package.)
See also the restrictions and limitations on native methods.
In addition, there is a separate and distinct Java 2 Standard Edition, v. 1.3.0, implementation available for, and distributed with, the Caldera OpenLinux Workstation 3.1 and OpenLinux Server 3.1 operating system products. It too is a full implementation of the Sun Microsystems Java 2 Platform. The major internal difference between that Java implementation and this one is that the OpenLinux implementation uses by default the Sun HotSpot virtual machine, while the Caldera UNIX operating systems implementation uses the Sun "classic VM" virtual machine together with a JIT compiler. For most applications, the HotSpot virtual machine will show better performance than the classic VM/JIT combination.
On Open UNIX 8
when the Linux Kernel Personality feature
is installed, it is possible to run the Java implementation
for OpenLinux
while in the UNIX environment.
To do this, access the J2SE 1.3 for OpenLinux
implementation through the /linux filesystem, as in this example:
$ /linux/opt/java-1.3/bin/java -version java version "1.3.0" Java(TM) 2 Runtime Environment, Standard Edition, root-09Mar2001-22:12 Java HotSpot(TM) Client VM, Caldera Systems, mixed mode
(You cannot currently use the more natural /linux/usr/java/bin/java
because of a symbolic link not working across the filesystem divide. Of course,
you can also use the linux command to go into Linux shell mode,
after which you can access Java using /usr/java/bin/java.)
The J2SE 1.3 for Caldera UNIX implementation described in these Release Notes may be still accessed as well, in the normal manner:
$ /usr/java/bin/java -version java version "1.3.0_02" Java(TM) 2 Runtime Environment, Standard Edition (build SCO-JDK-1.3.0_02:-010416-03:42) Classic VM (build SCO-JDK-1.3.0_02:-010416-03:42, native threads, sunwjit)
Options can be given to the J2SE 1.3 for OpenLinux implementation to select the HotSpot client compiler, the HotSpot server compiler, the HotSpot interpreter, or the classic VM interpreter (native threads or green threads). No JIT compiler is available for the classic VM in J2SE 1.3 for OpenLinux.
If native methods are used in conjunction with J2SE 1.3 for OpenLinux, they must be built with the GNU GCC compilers present in the OpenLinux distribution. They cannot be built with the Open UNIX 8 GCC compilers or with the OUDK compilers.
The J2SE 1.3 for OpenLinux implementation cannot be used on the SCO OpenServer 5 platform; the J2SE 1.3 for Caldera UNIX implementation described in these Release Notes is the only Java implementation available for SCO OpenServer 5.
Copyright © 2002 Caldera International, Inc. All Rights Reserved.
Caldera, OpenLinux, SCO, SCO OpenServer, UnixWare, and Open UNIX are trademarks or registered trademarks of Caldera International, Inc. in the U.S.A. and other countries.
The Santa Cruz Operation, Inc., SQL-Retriever, Tarantella, and Tarantella Enterprise 3 are trademarks or registered trademarks of Tarantella, Inc. in the U.S.A. and other countries.
Sun, Sun Microsystems, Java, Java Development Kit, JDK, JavaBeans, JDBC, and HotSpot are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States and other countries, and are used under license.
UNIX and Motif are registered trademarks of The Open Group in the United States and other countries. Intel is a registered trademark of Intel Corporation. NonStop is a registered trademark of Compaq Computer Corporation. X Window System is a trademark of the Massachusetts Institute of Technology. Linux is a registered trademark of Linus Torvalds.
The Santa Cruz Operation, Inc. and SCO Skunkware are not related to, affiliated with or licensed by the famous Lockheed Martin Skunk Works®, the creator of the F-117 Stealth Fighter, SR-71, U-2, VenturestarTM, DarkstarTM, and other pioneering air and spacecraft.
Caldera International, Inc. reserves the right to change or modify any of the product or service specifications or features described herein without notice. This document is for information only. No express or implied representations or warranties are made in this document.