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Module 7: JCL GDG

Characteristics of GDG

  • All datasets within GDG share same name except the last qualifier which is made of generation number and version number
  • Generation number is automatically assigned by Operating System
    Syntax:- GaaaaVxx
    aaaa - absolute generation number, 0001 to 9999
    xx - version number, 00 to 99
  • Datasets within GDG can be referenced by its relative generation number.
    • GDGBASENAME(0) references current generation
    • GDGBASENAME(-1) refers to generation just before the current generation
    • GDGBASENAME(+1)refers to the next generation data set just after the current one
  • It can also be referenced by actual name of generation dataset for example:- ‘PAYROLL.SALARY.MONTHLY.G0001V00
  • Generations are updated only at the end of the job, meaning:-
    • JOB STEP1 creates one generation, code it as GDGBASENAME(+1)
    • JOB STEP2 creates one more generation, then you have to code it as GDGBASENAME(+2) because the (+1) is not yet promoted to current generation.
    • For any executing job the current generation remains same until it ends. So in above case GDGBASENAME(+2) will get promoted to current generation only after execution of job

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