New Users

Hi, and welcome to LMS3270. I'm the admin and will help you get started with us.

First, I'll talk about starting to learn mainframe technologies and general tips on how to program COBOL based business applications. Then, I'll explain how to access our mainframe so you can get hands on experience writing and running your own programs.

The Mainframe is a complex environment. Its made up of large computer(s) with many attached devices costing millions of dollars. Most mainframes run IBM's Operating System called z/OS. It's hard to access a mainframe to learn how to use it. That is where we come it. We lease time with a larger firm to provide you low-cost access to a development environment with all the standard tools used by programmers across the world.

You access a mainframe from a PC using software called a "3270 Terminal Emulator". Once you have access to a mainframe like ours you'll need to learn several things before you can start coding programs. For example, programmers build and run their code using a mainframe application called TSO & ISPF. Its like x-windows on Unix or Windows on Intel PC's. TSO is like a unix shell prompt or the DOS prompt in windows. ISPF is like a windows-based system. The mainframe does not provide graphic displays with mouse interaction. Instead its screens are text based and you use your keyboard to move the cursor.

In ISPF, there are many tools. The 3 most important things to learn in ISPF is how to navigate, the Editor and how to submit jobs (run programs) and view output (logs).

Then you have to learn the filesystem. Unlike UNIX or Windows, mainframes use pre-defined files structured in various ways. For example, a simple text file is called a sequential data set (lets just called them files). A file can have records that are fixed or variable in length. Files take up a specific amount of space on their hard drive that are called DASD (Direct Access Storage Devices - pronounced daz-dee). Most companies with mainframes have hundreds to thousands of DASD's and many-many files . Another popular type of file structure is a Library, also called a PDS for Partitioned Data Sets. PDS's have members. They are like WIndows folders. Programmers use PDS's to store their code. Most modern mainframe applications use databases like DB2 which also uses DASD.

You'll need to understand how data is encoded. The mainframe uses a system called EBCDIC (Extended Binary Coded Decimal Interchange Code - pronounced "ehb-suh-dik"). This is very different from UNIX and WIndows which encode data in ASCII. EBCDIC is a binary coding system using an 8-bit binary number (a string of eight 0's or 1's). 256 possible characters (letters of the alphabet, numbers, and special characters) are supported. Checkout more at https://en.wikipedia.org/wiki/EBCDIC.

Beginners should have a general understanding of the Operating System and its core components. This is maintained by System Administrators. There are many type of Admins. In addition to managing the OS, Admins manage TSO/ISPF, RACF (mainframe Security), JES the Job Entry System to run programs, DB2 Database, Networks, CICS and many other system software.

These are some of the core concepts a mainframe programmer is aware of . Then there is the ability to design and write programs. In the mainframe the most popular programming language is COBOL. It is a very simple, non object-oriented, language used since the 1960's. COBOL programmers, build Batch or Online applications that use Databases, file systems, Networks, Message Queue and API's to many services.

I hope this gave you an idea of what you'll need to start learning how to use a mainframe. To learn more go to LMS3270.COM and shop for access to get hands-on lessons or browser our tech library for free.