z/OS ICF Catalogs

The ICF (Integrated Catalog Facility) Catalog setup is one of the strengths of the z/OS operating system. To find a file, you do not need to know anything about directory structures or paths, in fact both those terms are meaningless under z/OS. All you need to know is the file name. A big advantage of this is that if you move a file to a different volume there is no need to change JCL or batch scripts. Usually every file can be located by its name, and all files have unique names. z/OS file names, or rather dataset names, consist of a number of 1-8 character qualifiers, separated by periods. So a typical file might be called 'sysinf.job.library' The 'sysinf' part of the name is called the high level qualifier, and is an important part of the cataloging process

The ICF consists of a number of components. The Basic Catalog Structure (BCS) is the ICF catalog. This is a KSDS VSAM cluster and as mentioned above, the main function of an ICF catalog is to point a dataset name to its volume name.
The VVDS is an ESDS VSAM cluster that contains extra data about VSAM and DFSMS managed data. Both these components are described in the next section.

The ICF Catalogs page describes how an ICF catalog works

The Catalog structure is complicated and can go wrong. The Fault finding page describes typical catalog problems, how to find them and how to fix them.

The ultimate catalog fix is to recover it, but to do that you need good backup. The Backup and Recovery page describes this.

While ICF catalogs are a strength, they are also a weakness as if they fail then data cannot be accessed. The final section on Catalog Products details lots of products to help manage catalogs, both IBM and third party.

Alternatively, use the left hand frame to navigate between pages.

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Managing VSAM files

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I retired 2 years ago, and so I'm out of touch with the latest in the data storage world. The Lascon site has not been updated since July 2021, and probably will not get updated very much again. The site hosting is paid up until early 2023 when it will almost certainly disappear.
Lascon Storage was conceived in 2000, and technology has changed massively over those 22 years. It's been fun, but I guess it's time to call it a day. Thanks to all my readers in that time. I hope you managed to find something useful in there.
All the best