Tutorial approach



Opposite is an explanation of the approach taken to arrive at a set of working programs, which required REXX routines as drivers, an Assembler interface program (middleware if that term is prefered), and HLL programs written in COBOL.

How the subject was approached.



These were the basic steps taken.

  • Phase 1 - The Benchmark
    • Code a small COBOL program to increment and display a counter
    • Code a REXX routine which used LINKPGM to invoke the above directly
  • Phase 2 - Pre-initialisation
    • Code an Assembler program to drive the LE pre-initialisation program CEEPIPI
    • Code a REXX routine which used LINKPGM to invoke the Assembler program, which in turn invoked the COBOL program
      At this point the pre-initialisation concept was working.
  • Phase 3 - Adding a second parameter
    • Code a second COBOL program to accept two parameters to test passing data back to REXX
    • Modify the Assembler program to handle two parameters as input
    • Code a second REXX routine to pass two parameters again using LINKPGM
      At this point the ability to pass data back and forth to the HLL program was confirmed.
  • Phase 4 - Do something useful
    • Code a third COBOL program to perform queries against a VSAM KSDS
    • Modify the REXX routine to ensure the receiving variable was large enough
    • Modify the Assembler program to invoke the VSAM driver
      At this point the ability to process a VSAM KSDS from REXX was established

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