Generation Data Groups (GDG)

GDG is a group of datasets that are related to each other chronologically or functionally.Each of the dataset is called a generation number.
The generation number distinguishes each generation from others.
In order to create a GDG the following things must be specified to the OS :
1)the name of the GDG
2)The number of the generations that are to be retained
3)Whether or not the oldest generation is to be uncataloged once the limit for the number of the generations that are to be retained is reached.
4)Whether or not all generations are to be uncataloged once the limit for the number of the generations that are to be retained is reached.
5)whether or not an entry for a dataset that is deleted from a GDG is to be uncataloged from the volume it resides on.

Following is the example of the JCL whcih creates a GDG Base.

After creating the base you have to add a Generation to it with the following JCL

You can also alter and delete the GDG parameters using the following control card.
//SYSIN DD *
ALTER ABCDE.USERID.GDG LIMIT(255)
/*
//SYSIN DD *
DELETE (ABCDE.USERID.GDG)GDG
/*

jcl_fun

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