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A discussion of what buffers and blocks are and how they can make a difference as to how efficiently a mainframe computer can read and write datasets.

Buffering and Blocks

All programming languages have what are known as reserved words. These are the words to which the language has assigned special meanings and they generate the basic structure of how the language itself works. You can’t use reserved words for any purpose within the language than that for which their use is reserved. Not all reserved words are necessarily obvious since most languages allow certain statement constructs that almost never get used and sometimes there are words reserved for use in those statements that you wouldn’t expect. For those interested in programming in COBOL, here’s a list of the Reserved Words for that language.

Judging by the number of computer questions that I receive where the sender has selected the mainframe category that in fact have nothing whatever to do with mainframe computers, I’d say that there are a lot of people who have no idea what a mainframe is.

Well one of those people finally decided to ask the question giving me the opportunity to explain how to tell if the computer you want to ask a question about is a mainframe. So now there is no excuse for anyone to make that mistake again is there?

What is a Mainframe?

The most useful command in the ISPF editor on mainframe computers id the Find command. This command contains options that allow you to be very specific about exactly what it is that you are searching for and what part of the document that you want to search for it in. In this article I cover all of the options for how you can flexibly define what you want it to search for as well as how to limit the search to selected columns and or rows of the file.

The ISPF Find Command

One of the main ways that mainframe computers provide for interactive programs is via CICS (pronounced “kicks”). This reference page lists all of the common commands that you are likely to need to use in writing a CICS program including all of the parameters that can be specified with these commands.

CICS commands

For some unknown reason when I first started writing mainframe JCL articles I ended up writing quite a few about Generation Data Groups of which this one was the first.

What is a GDG?

Not all of the new pages on the site are web related. Here’s one where I answer a question regarding GDGs on mainframe computers.

With a Generation Data Group you have both the individual datasets as well as the catalog that groups them together. The purge and force keywords determine whether one, the other, or both are deleted when you run a delete request.

Deleting GDGs

The mainframe sort utility program can do a lot more than just sort the records in your file. It can also be used to test for and remove duplicates.

Removing Duplicates Using DFSORT