IBM S/390 mainframe COBOL source code

Question

We have an S/390 mainframe at my new job that’s been running COBOL applications since the late 90’s. The mainframe is getting old enough that we need to migrate to a newer system. We’re a small enough business that we can’t warrant spending the money to upgrade to new mainframe hardware and the program logic has been a constant work in progress for 30+ years, so it has a lot of functional value. I’ve been considering moving the functionality to a Linux machine and using something like OpenCOBOL to recompile as an executable binary instead of trying to rewrite it in a newer language. I haven’t messed with a mainframe enough to have any clue how or where to access this information and the gentleman that wrote all of the programs is unfortunately no longer with us. I’ve read that SSH is an option, but I’m not even sure how to get the ball rolling on that with a mainframe. I use Linux on a fairly regular basis, so I’m familiar with SSH, but from my understanding those mainframes aren’t a simple OS that you can merely connect to and navigate the file system to retrieve data like we can in modern operating systems. Can anyone give me some pointers to get a sense of direction for accessing the source code for the COBOL programs? Are there default locations that they are stored, etc.? They’re somewhat simple programs that don’t use any DB2 functionality and will hopefully compile on a different system with relatively minimal debugging and fixes. I’m certain that I’ve left out necessary information that would help getting an answer to this question, and I can provide any additional information that is needed to help you all help me. I suspect that SSH isn’t enabled by default, but maybe I’m wrong there too. Any assistance is greatly appreciated. Thanks everyone!

Answer 1

Although not a programming question I'll provide some guidance I think might help you.

First, this is a business decision about where to invest.

• Do we upgrade the system to a newer model and upgrade some software and acquire the skills to keep the system running? (System Programming, OS upgrade and cost of migration, newer platform (used z13 could be an economical option, storage systems to support the mainframe)
• Migration of existing workloads to other platforms. (Cost to migrate code, sizing of performance needs, new technologies to replace existing access methods like VSAM or dare I say ISAM if the applications are old enough)
• Status Quo ... leave things where they are and keep the lights on

In evaluating any option you have to assess the risk to the business and what would a disruption cost? IMHO, its less about a technology like SSH or COBOL on Linux but requires some serious assessment of the current state, the acceptable to be scenarios and the cost of pursuing one of those options.

My comments are not intended to instill fear but provide a framework of how do I approach analyzing a challenge of this magnitude.

Answer 2

There is no default location where source code is stored on z/OS (it is z/OS you're talking about, right?). Source code is usually stored in PDS data sets. The naming of those depends on the installation, i.e. the company, and whether or not any software like Endevor, ChangeMan, etc. is being used to maintain the sources.

Since this is old z/OS (OS/390) COBOL code, chances are the code is making use of OS specifics such as record level I/O, VSAM data sets, etc. These are the parts that will not work on a non-z/OS platform without major rewrite. So, you will need to look into the sources.

SSH is available on z/OS, but it needs to be configured and enabled. You need to check with your z/OS sysprog. FTP, and NFS are other options, but again, they need to be configured and enabled.

Transfering the sources is the least of your problems, I'd say.