GDG Generations and PDS Members

Why should we go for generations in GDG when the members in PDS can do the same work?

Questions by shri_shabi

Showing Answers 1 - 5 of 5 Answers

You COULD do this but it will cause much more manual intervention.? Every time you run the job, you will have to change the member name.? You have to explicitly code the reference which is known as absolute reference.

GDG's add the convenience of relative reference.? To access the most recent version, you code "(0)".? To access a previous version, code "(-1)". To create a new version, you code "(+1)"?
To accomplish the same tasks using PDS members, you would have to change the code for each of the above tasks.


  • Sep 3rd, 2010

GDGs are useful because you can easily keep track of datasets. It is also useful in that no JCL will require changing as the job is run from one time to the next. A problem with using PDS members is in the naming. You can add a step to delete the member at the end of the job - provided you are sure you will never need it again. Another common method would be to delete the member as a first step. If you are using different names - this can become complicated because depending on how you generate the name you may end up with a conflict between runs (ie if it includes the date, you have problems if you run the job multiple times per day, you could add time but again you could have issues depending on what your resolution is. Another issue is to make sure that you are using the correct member.) GDGs have rules you can set up to automatically drop generations. You can also use GDGs for easier restart or recovery.  

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  • Jan 13th, 2011

What is the difference between maintaining our accounts in notebook and MS-excel? Excel makes the job easy for us. The same thing is with GDG.

If you are maintaining your employees records. Each month some employees are resigning their jobs or changing their contact address or number and you are recruiting new members every month. If you are doing this job with pds members then you should give different name to the file by editing the program. Further if some other program is using this file as input then you should remember the name given to the recently created file. And if you only want the records of last three months then you should keep track of the members being created and you should delete the files which are older than three months.

All the above tasks become easy with GDG. Here current version of GDG is represented as GDG(0) and if you want only last three updates then LIMIT(3) should be specified. Moreover there is no need to edit the program while creating a new GDG version.


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  • Sep 7th, 2019

Generation Data Groups (GDGs) are group of datasets related to each other by a common name.
All datasets have the same name(GDG base and its relative number) and is easy to keeps track of adding new and retaining previous generations and deleting unwanted generation.

Unlike GDG, PDS members works like a PS file.

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