Issues and limitations on z/OS
Known issues or limitations that you might encounter in specific z/OS® system environments, or configurations.
- Java™ 2D rendering pipeline
-
The improved Java 2D graphics pipeline, based on the X11 XRender extension, accelerates rendering using hardware support. However, the XRender library is not supported on the z/OS operating system, and is therefore not available in this release. If the new pipeline is not present, Java 2D uses the existing X11 pipeline.
- Limitation of class path length
-
If there are more than 2031 characters in your class path, the shell truncates your class path to 2031 characters. If you need a class path longer than 2031 characters, use the extension class loader option to refer to directories containing your .jar files, for example:
Where <directory> is the directory containing your .jar files.-Djava.ext.dirs=<directory>
Messages written using stdout/stderr may not be redirected when freopen() is used
Messages that the JVM writes to stdout / stderr might not be redirected to the new file if the Java app uses the C®/C++ freopen() function to redirect stdout / stderr streams from a file of one type to the other. To fix this problem, set the com.ibm.writeToStandardOutputsUsingStreams system property to
true
when you start the JVM. This property specifies that the output is written by using file streams, which support the redirection of data between MVS datsets and USS zFS files.Note: This setting also changes the default buffering behavior fromno buffering
toline buffering
, and output might not be produced promptly. To counter this issue, disable buffering by using the setbuf() or setvbuf() functions after calling the freopen() function.- Class
java.awt.Robot
is not supported -
The
java.awt.Robot
class is not supported on z/OS systems. Java programs that use theRobot
class will not run correctly on z/OS systems.
Other issues
If you find a problem that you have been unable to solve, see https://www.ibm.com/systems/z/os/zos/tools/java/index.html for advice and information about how to raise problems.