Application programming on z/OS
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Application development tools

Application programming on z/OS

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Producing well-tested code requires the use of tools on the mainframe.

The primary tool for the programmer is the ISPF editor. When developing traditional, procedural programs in languages such as COBOL and PL/I, the programmer often logs on to the mainframe and uses an Interactive Development Environment (IDE) or the ISPF editor to modify the code, compile it, and run it. The programmer uses a common repository (such as the IBM® Software Configuration Library Manager or SCLM) to store code that is under development. The repository allows the programmer check code in or out, and ensures that programmers do not interfere with each others' work. SCLM is included with ISPF as an option from the main menu.

For purposes of simplicity, the source code could be stored and maintained in a partitioned data set (PDS). However, using a PDS would neither provide change control nor prevent multiple updates to the same version of code in the way that SCLM would. So, wherever we have written "checking out" or "saving" to SCLM, assume that you could substitute this with "edit a PDS member" or "save a PDS member."

When the source code changes are complete, the programmer submits a JCL file to compile the source code, bind the application modules, and create an executable for testing. The programmer conducts "unit tests" of the functionality of the program. The programmer uses job monitoring and viewing tools to track the running programs, view the output, and make appropriate corrections to source code or other objects. Sometimes, a program will create a "dump" of memory when a failure occurs. The programmer can also use tools to interrogate the dump output and to trace through executing code to identify the failure points.

Some mainframe application programmers have now switched to the use of IDE tools to accelerate the edit/compile/test process. IDEs allow application programmers to edit, test, and debug source code on a workstation instead of directly on the mainframe system. The use of an IDE is particularly useful for building "hybrid" applications that employ host-based programs or transactional systems, but also contain a Web browser-like user interface.

After the components are developed and tested, the application programmer packages them into the appropriate deployment format and passes them to the team that coordinates production code deployments.

Application enablement services available on z/OS® include:

  • Language Environment®
  • C/C++ IBM Open Class® Library
  • DCE Application Support1
  • Encina® Toolkit Executive2
  • C/C++ with Debug Tool
  • HLASM Toolkit
  • Traditional languages such as COBOL, PL/I, and Fortran

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