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
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