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manual abstract
Pipe I/O
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TMF transactions (
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com.tandem.tmf package)
JToolkit provides a thread-aware API for performing I/O to Enscribe files, $RECEIVE, and Pathway servers by
using Pathsend procedure calls. For more information, see the JToolkit Programmer's Reference.
OSS file I/O operations are not thread-aware. These operations block the entire Java process for the duration of the
operation. The operations that block the whole program rather than just the thread invoking the operation can be
safe when invoked in a Java multithreaded program if the operation:
Does not take a long period of time (more than one second) to complete. For example, the OSS environment
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has file caching enabled by default so that a small I/O completes once the data is in the cache. For more
information, see "Managing Files" in the OSS Programmer's Guide.
Does not wait for input from the user.
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Does not wait for a contended object. For example, acquiring a lock.
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Is in code that is not in the normal course of operation. For example, occurs only during error handling.
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Since I/O to OSS files is not thread-aware, do not create a Java thread to perform I/O to an OSS file. In fact,
creating a new thread for performing a non thread-aware function introduces a performance overhead for no gain.
Threading Considerations for Native Code
All threaded code should be written in Java rather than native code. If a user native library linked into Java creates
a thread, non thread-aware operations executed in the user library might impact the operation of the Java virtual
machine. If the user library creates multiple user threads, the program needs to be all the more careful to ensure
that the operations performed in the user threads are thread-safe on the NonStop system.
You need to consider the issues discussed below when using threads in native code linked to a Java program on a
NonStop system:
NonStop Server for Java 5 does not use the POSIX threads SRL.
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Instead, NonStop Server for Java 5 contains its own version of POSIX threads. Therefore, your code should
include the Standard POSIX Threads header files shipped with NonStop Server for Java 5. The header files
for this version of POSIX threads can be found in the directory:
[install-dir]/java/include/oss
where install-dir is the NonStop Server for Java 5 installation directory.
Creating a thread for a task does not make the task run faster.
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The NonStop system does not have an implementation of native threads; threads run at a user level. Even on
a multiprocessor NonStop system, all threads in a process are executed in the same processor as the process.
If you create a thread whose only purpose is to run a certain task, the thread-creation overhead makes the
task run marginally slower than the same task being performed without creating the thread.
The thread-scheduling algorithm is not preemptive.
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A thread executes until it explicitly yields. For more information, see the discussion of Thread Scheduling.
In a very long-running, CPU-intensive thread, having your native code occasionally invoke the
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yield()
method allows timer completions and I/O completions to be detected. Invocation of timer callbacks and
detection of I/O completions can be severely impacted by long-running threads.
Be familiar with the issues discussed in the Application Programming with Standard POSIX Threads
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section of the OSS Programmers Guide.
...Other models in this manual:
Desktops - HP Integrity NonStop J-Series (444.95 kb)