I am working for an insurance company with about 180 employees. About half of these employees register something in their Claims system (sales, consulting services, claims handling etc.). The core system is written in Cobol and runs on a mainframe. Recently they bought a new mainframe for 100.000$ because they said that their old one ran on 100% constantly. After they got the new mainframe, I spoke to an employee working in the statistics department, who said that they run one to two statistics queries overnight on the mainframe, so as to not interfere with normal work on the server.

My question is: How does the performance of a mainframe compare to desktop computers. I am quite sure that I could set up a 400 dollar PC with a database and have that handle 90 employees that are writing names and addresses of customers and searching through a databaes that cannot be that big. With a bit of replication and stuff I believe I could achieve excellent performance. What am I missing here? Are mainframes always like this or is this a sign of a poorly implemented CRM system?


Unlike desktops mainframes are, usually, EXTREMELY available/stable and if designed well fast as hell at large loads - but if the software is badly written they can be as slow as a desktop machine.

The main issue is often that there already exists a business-critical system that runs on an old code base, so when the hardware becomes too slow or unsupportable the business has to decide whether to rewrite their systems in a more modern and better performing way for new hardware or simply shift the old software and its data to a slightly more modern but backwardly compatible hardware. It all comes down to risk to the business and very often people go with the latter approach, don't forget that to most businesses IT is an inconvenience not the raison d'etra.

The thing to bare in mind is that even if you do buy a $400 box you still have to add in the software and licences, the costs of development, testing and rollout staff, support costs, probably some form of backup system to deal with the flakiness of $400 hardware plus all the other hidden costs and importantly there's still no guarantee that it will function, perform or be stable - give that option or spending $100k (which isn't much at all for that level of kit) I think I'd have bought the mainframe too.

  • Thanks for an excellent answer. What you say makes perfect sense. In the case of this company the codebase is probably old as the IT-department has been underfunded for years and the company has existed for half a century. There should be a huge business potential if one could rewrite the old code and prove that the new code ALWAYS gave the same results. – David Sep 18 '09 at 10:26

Performance is really quite difficult to compare. In sheer computational speed, a cheap x86 box can be quite competitive. Mainframes really excel at parallel operations and tend to have MUCH better I/O throughput. All the extra money buys electronics that make multitasking much smoother and more efficient as well. When you're used to working on high-end workstations and mainframes, switching to a PC feels very jerky and bursty, not at all smooth and fast like on the mainframe.


This is a case where TCO and risk comes in to play. They buy a mainframe for $100,000 and probably spend $25,000/year on mainframe/OS support and another $20,000 on support for their application.

Switching to a Unix or Windows server is tough; you're going to need one or more consultants to migrate your data safely, you need to evaluate multiple claims processing apps, and you need to train or hire 2-3 people to run the new system.

So if you're the CEO of a small insurance company, probably with an actuarial background; you're going to have a hard time moving a way from an adequate system with well-defined costs to a new system that may or may not be good, and whose short-term costs may be higher.

My wife works for a small municipal utility that replaced an AS/400 billing system last year -- that was purchased in 1989! (because IBM was out of parts and would no longer support it) From their point-of-view, it was like a washing machine -- it just sat there and hummed. If it broke, it would call IBM and they would show up to fix it. They are really unhappy with the replacement Windows system because the backup process sucks in comparison to AS/400 and someone needs to check the system once a week; no more "phone home".


Just as a brief extension to the chosen answer, mainframes are designed to run at full tilt without degradation of performance. I know that the IBM Z series in particular is perfectly capable of doing this, but doesn't come down to buying new hardware, since all new Z boxes are essentially the same with regards to CPU capabilities, but are software limited for cheaper options. So to upgrade, it's just a quick phone call to IBM to up the performance.

  • You can even get extra performance for your peak processing days, if you have seasonal variations in load. – Anthony Giorgio Sep 20 '11 at 13:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.