Define or Alter a GDG

Use Host Explorer's "Define" functionality to create a new generation data group (GDG) and define all values for it. A GDG contains generation datasets (GDSs). Use the "Alter" functionality to modify a GDG's value.

To define a GDG

1. Do one of the following:

   1. • From the File menu, select New>Generation Data Group. On the Select Host page of the Define Generation Data Group wizard, select or configure the desired host.
      • Right-click the z/OS Datasets node and select Allocate/Define>Generation Data Group.

   The Define Generation Data Group page or dialog box appears.In the GDG name field, enter a name for the new GDG. The maximum number of characters allowed is 35.

2. In the GDG name field, enter a name for the new GDG. The maximum number of characters allowed is 35.
3. Optionally, in the Owner field, enter the ID of the owner of the GDG.
4. In the Maximum limit of generations field, enter the highest number of generation datasets that can be associated with the GDG being defined. When using z/OS 2.2 or higher, the maximum is 999. When using a version of z/OS below 2.2, the maximum is 255.
5. In the Empty processing when limit is exceeded box, select the action to be taken on the generation datasets within the GDG when the specified limit is exceeded:
   • Remove the oldest generation (default)
   • Remove all generations
6. Optionally, to delete a generation dataset from all disks it occupies when the generation dataset is uncataloged from the GDG due to empty processing, select the Scratch generation dataset on empty processing check box.
7. Optionally, to immediately delete a generation dataset when the limit is exceeded (regardless of the dataset's expiration date), select the Override expiration date and purge immediately upon scratch check box. This check box is only enabled if the Scratch generation dataset on empty processing check box is selected.
8. In the Dataset allocation ordering box, select either the LIFO (newest to oldest) or the FIFO (oldest to newest) button to indicate the order in which GDSs for this GDG should be allocated.
9. Click Finish. A message indicates that the GDG has been defined. The GDG appears in Host Explorer under the z/OS Datasets node.

To alter a GDG

1. In Host Explorer, right-click the GDG base dataset name and select Alter.
The Alter Generation Data Group page or dialog box appears.
2. Modify any editable fields as desired.
3. Click Finish. Any updates are reflected in the Properties view for the GDG.