MVS JCL in Plain English

JCL is the stuff of nightmares for many programmers and operators. This book explains JCL in such a way as to have it make sense.

This book will help you learn how to to tell the IBM MVS mainframe computer how and when to execute your programs. To do this you use a language called JCL, for Job Control Language. You use JCL to tell the mainframe how much memory and other resources your programs will need, how long each program should be allowed to run, what order to run the programs in, where to get the input data, where to put the output data, and so on. JCL controls almost everything related to running programs on MVS.

If you have a comfortable understanding of ordinary English language and are looking for a quick and easy way to learn JCL, this book is for you.

If you already know a little JCL and what you really want is a handy reference guide to bail you out on commonly occurring problems with JCL, you're in luck again, this book is for you there too.

If you're looking for an introduction to some of the more advanced and obscure tricks you might have seen people use in MVS, you guessed it, this book is for you on that as well.

How can this book do all that at once? Because, contrary to its reputation, JCL is not particularly difficult; it just has esoteric aspects that make it seem difficult if you have nobody to explain things. Once explained, all seems clear, as with most things.

This book can be used as a reference book, there are numerous examples and the index will assist you in finding what you are looking for when you need to find a solution to a problem. You can also read the book as an introductory text, from start to finish. Things are explained in plain ordinary language, so even if you have never before seen one line of JCL, you should have no trouble with the text; and by the time you get halfway through the book people should be starting to see you as an expert, probably to your great surprise. When you read the book straight through in this way, you will come across a lot of obscure but useful information to help you in your routine use of MVS.

JCL is a language like any other. If you travel to an area where you do not speak the language, you get a certain amount of satisfaction when you are able to make yourself understood using that language, be it to make a phone call, or ask for directions, or just to ask the price of something. The more you use the language the more you feel at ease using it. Having good guidebooks saves you a lot of learning time. And who doesn't love it when other people start mistaking us for locals and asking us the directions? That's the same sort of feeling you'll get the first few times your co-workers ask you to help them with their JCL problems; and that will start happening a lot sooner than you might think, because,contrary to appearances, most of them don't know much more about it than you do now. That's why they have so much trouble explaining it to you. That's why you want a good book on it now.

JCL is not generally taught in schools and Universities, so people who need to use JCL generally have to learn it on the job. For the most part they have a difficult time, largely because the people they learn from don't have a good grounding in JCL either. Those other people only learned enough to get by when doing a few things they needed to do; and those few things may not be the same things you need to do now. So your co-workers can be of only limited help to you with learning JCL.

Whether your job is programming, operations, or anything else, whatever your reason for wanting to learn JCL, this book is designed to help you. It will help you learn JCL in the first place and thereafter it will be a useful reference you can keep coming back to, like an old friend, to help you out when you get into trouble.

The book is organized into four main sections. 'Section 1. Getting Started’ is made up of Chapters 1 and 2. Chapter 1 is an introduction to the history of JCL and Chapter 2 explains the basic structure of the language. Yes JCL does have a language structure, and when you understand that structure you will learn the language much more quickly and it will start to make sense. You might skip Chapter 1, but read Chapter 2.

‘Section 2. The Data’ spans Chapters 3 through 10. This section explains how data is organized on MVS and how to define and manipulate collections of data. Many people make their first changes to JCL because there is a requirement to have a program run with different data than usual. For example, if a program has been using a certain data file for reference purposes, say a list of products and the associated prices, and one day for some reason a different reference file has to be substituted, say a new price list has come out, then a simple change to the JCL can bring the new file into use. You will learn how to make this type of change, and many others, in Section 2.

‘Section 3. Running the programs’ is Chapters 11 through 14. This section will give you information about controlling the conditions of program execution (how much time and memory your program will be allowed to use, dependencies on other programs finishing first, and so on) and about creating your own JCL Procedures. A JCL Procedure (or PROC) is a collection of JCL put together for some repeatedly occurring purpose, like a program written in JCL. This can be a powerful tool for automating processes under MVS.

‘Section 4. Advanced JCL’ is composed of Chapters 15 through 20. This section is particularly useful for those who want to know some of the more advanced (and yes, usually esoteric) aspects of JCL. There is also a Chapter that discusses some common standard programs you will use under MVS -- such as the various Utility programs you can use to copy data, sort data, rename files, extend or compress or merge files, and so on.

By the way, MVS/ESA is covered in the book. The new JCL features of ESA are explained and examples are provided. You will be pleasantly surprised how easy JCL actually is to learn.