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This is an example of a COBOL program and JCL that will create and process a Generation Data Group or GDG on a Mainframe System with ZOS or a Linux. Generation Data Groups (GDGs) are group of datasets related to each other by a common name. The common name is referred as GDG base and each dataset. JCL & VSAM: Hi all, I want to know the major difference between the dataset and GDG. reagrds akshatha.

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We have made a significant effort to ensure the documents and software technologies are correct and accurate. In the world of programming there are many ways to solve a problem. A generation data group GDG base is allocated in a catalog before the generation data sets are cataloged.

Hence, the dataset is deleted when the job completes execution.

IBM Utilities Tutorial – 04 : Generation Data Group – GDG – Mainframes

GV00 and so on. Since the DSN name is the GDG name without an appended GnnnnVnn segment each of the individual data sets or files will be processed as a contiguous file starting with the last created data set. To create a GDG Model, we simply need to create an empty dataset, maainframe space mainframr, and bearing the DCB of the generations, you want to create.

JCL referenced the GDG as a group the output file should have all six records each of the individual data sets associated with the GDG has two 2 records. If the attributes and organizations of all generations in a group are identical, the generations or individual data sets may be retrieved together as a single data set.


What if the customer wanted a report which shows him, his Bank Account Statement of the last 6 months? A typical sequence of events is to submit the jobs described in Steps to Enterprise Server and then review the results.

Here, we have kept limit as 3. We’ll talk about the operating system, the software installed on a mainframe.

JCL – Defining Datasets

For example, the nainframe set name LAB. Copyright IBM Corporation SimoTime Technologies makes no warranty or representations about the suitability of the software, documentation or learning material for any purpose.

New system-managed data sets are always cataloged when allocated, with the volume assigned from a storage group. Explore the Glossary of Terms for a list of terms and definitions used in this suite of documents and white papers.

The preceding job uses the IEFBR14 program a system supplied program that simply does a return to caller with a return code of zero in conjunction with a DD statement to create the model. We specialize in preparing applications and the associated data that are currently residing on a single platform to be distributed across a variety of platforms.

Usually, for testing purposes or for an incident fix, there might be a need to use different datasets other than the ones specified in the cataloged procedure.

Suppose, the Credit Card Accounts have been updated till the month of July. SimoTime Technologies shall not be liable for any direct, indirect, special or consequential damages resulting from the loss of use, data or projects, whether in an action of contract or tort, arising out of or in connection with the use or performance of this software, documentation or training material.

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GDG 0mianframe versions are referred as -1-2 and so on. The two zeroes on the end of the name are mainframf to represent a volume number that is used when the file is stored on media requiring the use of multiple volumes.

If you have any questions, suggestions, comments or feedback please call or send an e-mail to: This means, a maximum of 3 generations will be stored in the GDG. This document and the links to other documents are intended to provide a greater awareness of the Data Management and Application Processing alternatives.

What is a VTOC? This means, all the generations within the GDG follow, the same record format, the same record length, the same block size etc. In other words, maunframe need to preserve the past historical data.

Program Input and Output.

IBM MAINFRAME: Diff between a GDG and a dataset

Generation data sets have sequentially ordered absolute and relative names that represent their age. Process a Generation Data Group. The relative name is a signed integer used to refer to the latest 0the next to the latest -1and so forth, generation. Therefore, adjustments may be needed to execute the jobs and programs when transferred to a system of a different architecture or configuration.

There are two ways to do this. The data will need to be transferred between the systems and may need to be converted and validated at various stages within the process. The model data only needs to be a VTOC entry and does not require disk space to be used.