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Status Delivered
Workspace IBM Java SDK for z/OS
Created by Guest
Created on Nov 4, 2020

RELATED IDEAS

Extend the JZOS ZFile class to include "unlocked" versions of read and locate for VSAM files

We've been prototyping and performance testing Java's ability to access VSAM record-oriented or Key Sequenced Data Sets (KSDS) using the ZFile class and now, our own home-grown functions based on the XL C/C++Run-Time Library – in particular, the locate and read family of functions.

It's seems very clear from our results that the ZFile.locate and ZFile.read functions will not scale in a multi-threaded fashion, i.e., while they are thread-safe, the underlying flocate() and fread() C functions are still blocking (or otherwise spending an awful lot of time) on a mutex that protects the file descriptor. We were under the impression that if we opened and allocated (from a pool), a discrete file descriptor for each thread, the mutex check would be “fast” and we would be able to scale with multiple threads. This is not the case.

When we substitute the ZFile locate and read methods with our own KSDS random reader based on the flocate_unlocked() and fread_unlocked() variants, we see good, near-perfect linear scaling. To preserve thread-safety, we continue to allocate a discrete, open file descriptor from a pool to each thread prior to performing the VSAM lookup.

Idea priority High
  • Guest
    Reply
    |     Aug 1, 2022
    .Two new APIs, locate_unlocked and read_unlocked, have been delivered in:
    -SDK80 SR6 FP35 version of IBM SDK for z/OS, Java Technology Edition, Version 8
    -GA version (11.0.0.0) Semeru Runtime Certified Edition for z/OS, Version 11.0.
  • Guest
    Reply
    |     Nov 4, 2020

    Due to processing by IBM, this request was reassigned to have the following updated attributes:
    Brand - Servers and Systems Software
    Product family - z Systems Software
    Product - JAVA
    Component - JAVA
    Operating system - IBM z/OS
    Source - None

    For recording keeping, the previous attributes were:
    Brand - Servers and Systems Software
    Product family - Programming Languages
    Product - C/C++ Compilers
    Component - Miscellaneous
    Operating system - IBM z/OS
    Source - None

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