IBM OS/390 User Manual
Chapter 4. Job Control Language (JCL) Differences and
Considerations
Considerations
The following sections describe the major tasks and considerations involved in
converting VSE JCL to MVS JCL and the differences between them. These
sections are divided into the following categories:
converting VSE JCL to MVS JCL and the differences between them. These
sections are divided into the following categories:
•
4.1, The Philosophy of JCL in System/390
•
4.2, High Level Similarities
•
4.3, JCL Differences Between VSE and MVS
•
4.4, JECL
•
4.5, VSE and MVS JCL Comparison Example
While this chapter describes the differences and conversion tasks, we
recommend that you take a class on MVS JCL. See Appendix A, “Education
Information” on page 535.
recommend that you take a class on MVS JCL. See Appendix A, “Education
Information” on page 535.
4.1 The Philosophy of JCL in System/390
Often, before discussing JCL systems and schemes, it is valuable to understand
why the System/390 (originally the System/360) operating systems incorporated
Job Control.
why the System/390 (originally the System/360) operating systems incorporated
Job Control.
In the era of the predecessor computer systems, for example the IBM 1400, 7080,
and 7090 systems, the concept of job control was just beginning. Application
program coding included explicit references to files and other system resources.
If a given program could be used with another file, the program often required
changes. Flexibility and the beginnings of resource reuse led to the concept of a
system facility that externalized the references from programs to other system
resources, whether they were other programs or data files.
and 7090 systems, the concept of job control was just beginning. Application
program coding included explicit references to files and other system resources.
If a given program could be used with another file, the program often required
changes. Flexibility and the beginnings of resource reuse led to the concept of a
system facility that externalized the references from programs to other system
resources, whether they were other programs or data files.
Job Control Language was developed as part of the System/360 architecture, to
address the requirement for reuse. The ability to use one program with different
files, and with different predecessor and successor programs, makes computer
programs much more usable. This ability to create jobs and steps is crucial to
the development of today
address the requirement for reuse. The ability to use one program with different
files, and with different predecessor and successor programs, makes computer
programs much more usable. This ability to create jobs and steps is crucial to
the development of today
′
s
″
Industrial Strength
″
information processing
technology.
As OS/390
′
s predecessors were being developed, it became obvious that the
smaller customers
′
needs required smaller systems. With the economics in the
information processing over 30 years ago, the smaller systems were too small in
terms of internal and external storage and processor power to provide the
minimum environment needed for OS/360.
terms of internal and external storage and processor power to provide the
minimum environment needed for OS/360.
VSE/ESA
′
s predecessors were developed to permit smaller customers
′
requirements to be met with the smaller systems then available. BOS (Basic
Operating System), TOS (Tape Operating System), DOS (Disk Operating System),
DOS/VS, VSE, and now VSE/ESA are the progression of operating systems
designed to
Operating System), TOS (Tape Operating System), DOS (Disk Operating System),
DOS/VS, VSE, and now VSE/ESA are the progression of operating systems
designed to
″
fill the hole
″
left by small processor requirements that could not
meet the minimum resource requirements of the OS/390 predecessors.
Copyright IBM Corp. 1998
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